minor #22303 Add \Traversable typehint to phpdoc (MetalArend)
minor #22303 Add \Traversable typehint to phpdoc (MetalArend)

This PR was submitted for the master branch but it was merged into the 2.7 branch instead (closes #22303).

Discussion
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Add \Traversable typehint to phpdoc

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Most of the times you use a DataMapperInterface, the first thing you do on the `$forms` parameter is `iterator_to_array`. However, as that variable is only hinted as `FormInterface[]`, and most IDE's and static analysers don't rely on code, but on the phpdoc...

Commits
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5310f11418 Add \Traversable typehint to phpdoc

docteurklein/symfony,yceruto/symfony,1ed/symfony,SaschaDens/symfony,1ed/symfony,Nyholm/symfony,mihai-stancu/symfony,fabpot/symfony,zorn-v/symfony,docteurklein/symfony,neemzy/symfony,csarrazi/symfony,nasimnabavi/symfony,mihai-stancu/symfony,jean-gui/symfony,gencer/symfony,andreia/symfony,zorn-v/symfony,jean-gui/symfony,inso/symfony,xabbuh/symfony,frankdejonge/symfony,ajgarlag/symfony,alekitto/symfony,pamil/symfony,d-ph/symfony,hason/symfony,OskarStark/symfony,Einenlum/symfony,OndraM/symfony,alekitto/symfony,localheinz/symfony,kbond/symfony,Simperfit/symfony,mvhirsch/symfony,Slamdunk/symfony,Engerim/symfony,bendavies/symfony,Amo/symfony,derrabus/symfony,garak/symfony,voronkovich/symfony,frankdejonge/symfony,Soullivaneuh/symfony,romaricdrigon/symfony,chalasr/symfony,WhiteEagle88/symfony,zorn-v/symfony,pamil/symfony,vincentaubert/symfony,dunglas/symfony,zorn-v/symfony,localheinz/symfony,frankdejonge/symfony,OndraM/symfony,romaricdrigon/symfony,teohhanhui/symfony,mweimerskirch/symfony,dmaicher/symfony,michaelperrin/symfony,codeclimate-testing/symfony,neemzy/symfony,fabpot/symfony,Triiistan/symfony,andrerom/symfony,Einenlum/symfony,okdana/symfony,smatyas/symfony,Aliance/symfony,mweimerskirch/symfony,c960657/symfony,Taluu/symfony,Amo/symfony,pierredup/symfony,Einenlum/symfony,teohhanhui/symfony,weaverryan/symfony,aeoris/symfony,maidmaid/symfony,Koc/symfony,DavidGarciaCat/symfony,curry684/symfony,symfony/symfony,lstrojny/symfony,symfony/symfony,ragboyjr/symfony,alekitto/symfony,apetitpa/symfony,tgalopin/symfony,sroze/symfony,e-moe/symfony,jzawadzki/symfony,ro0NL/symfony,mvhirsch/symfony,Triiistan/symfony,HeahDude/symfony,lepiaf/symfony,iltar/symfony,mpdude/symfony,inso/symfony,SaschaDens/symfony,josephdpurcell/symfony,SpacePossum/symfony,nicolas-grekas/symfony,jzawadzki/symfony,nasimnabavi/symfony,jderusse/symfony,ajgarlag/symfony,joelwurtz/symfony,jakzal/symfony,Simperfit/symfony,pyrech/symfony,Taluu/symfony,lepiaf/symfony,lepiaf/symfony,chalasr/symfony,kbond/symfony,Koc/symfony,phramz/symfony,ro0NL/symfony,alekitto/symfony,jvasseur/symfony,mihai-stancu/symfony,tgalopin/symfony,hason/symfony,tucksaun/symfony,lstrojny/symfony,Engerim/symfony,smatyas/symfony,Nyholm/symfony,backbone87/symfony,hhamon/symfony,hason/symfony,xabbuh/symfony,zcodes/symfony,gimler/symfony,paradajozsef/symfony,DavidGarciaCat/symfony,xabbuh/symfony,andrerom/symfony,bendavies/symfony,pierredup/symfony,maidmaid/symfony,hacfi/symfony,gencer/symfony,SaschaDens/symfony,jakzal/symfony,jderusse/symfony,dmaicher/symfony,OskarStark/symfony,gimler/symfony,shieldo/symfony,arjenm/symfony,Tobion/symfony,zcodes/symfony,MatTheCat/symfony,dmaicher/symfony,bendavies/symfony,nasimnabavi/symfony,Amo/symfony,Amo/symfony,hhamon/symfony,jvasseur/symfony,zcodes/symfony,vincentaubert/symfony,jvasseur/symfony,deguif/symfony,lyrixx/symfony,damienalexandre/symfony,zerkms/symfony,symfony/symfony,neemzy/symfony,c960657/symfony,Nyholm/symfony,sgehrig/symfony,tgalopin/symfony,dunglas/symfony,nicolas-grekas/symfony,jakzal/symfony,docteurklein/symfony,ro0NL/symfony,garak/symfony,mnapoli/symfony,Tobion/symfony,ragboyjr/symfony,Slamdunk/symfony,andreia/symfony,WhiteEagle88/symfony,WhiteEagle88/symfony,joelwurtz/symfony,andreia/symfony,Koc/symfony,deguif/symfony,pierredup/symfony,jean-gui/symfony,andrerom/symfony,lyrixx/symfony,arjenm/symfony,DavidGarciaCat/symfony,symfony/symfony,tucksaun/symfony,michaelperrin/symfony,Tobion/symfony,codeclimate-testing/symfony,ragboyjr/symfony,josephdpurcell/symfony,curry684/symfony,Strate/symfony,okdana/symfony,mvhirsch/symfony,OndraM/symfony,apetitpa/symfony,ajgarlag/symfony,joelwurtz/symfony,voronkovich/symfony,kbond/symfony,dunglas/symfony,ogizanagi/symfony,backbone87/symfony,mihai-stancu/symfony,gonzalovilaseca/symfony,curry684/symfony,sroze/symfony,joelwurtz/symfony,romaricdrigon/symfony,weaverryan/symfony,derrabus/symfony,pyrech/symfony,Tobion/symfony,mvhirsch/symfony,Deamon/symfony,michaelperrin/symfony,c960657/symfony,gonzalovilaseca/symfony,Pierstoval/symfony,SpacePossum/symfony,voronkovich/symfony,gnat42/symfony,derrabus/symfony,Deamon/symfony,OndraM/symfony,tucksaun/symfony,OskarStark/symfony,yceruto/symfony,SpacePossum/symfony,nicolas-grekas/symfony,Triiistan/symfony,SaschaDens/symfony,arjenm/symfony,stof/symfony,lstrojny/symfony,nasimnabavi/symfony,voronkovich/symfony,deguif/symfony,hhamon/symfony,okdana/symfony,michaelperrin/symfony,HeahDude/symfony,oleg-andreyev/symfony,mweimerskirch/symfony,ragboyjr/symfony,jean-gui/symfony,csarrazi/symfony,HeahDude/symfony,maidmaid/symfony,andrerom/symfony,garak/symfony,Slamdunk/symfony,inso/symfony,Soullivaneuh/symfony,inso/symfony,Pierstoval/symfony,mweimerskirch/symfony,Soullivaneuh/symfony,zerkms/symfony,paradajozsef/symfony,vincentaubert/symfony,mvhirsch/symfony,phramz/symfony,ogizanagi/symfony,Soullivaneuh/symfony,paradajozsef/symfony,Simperfit/symfony,teohhanhui/symfony,Soullivaneuh/symfony,Simperfit/symfony,csarrazi/symfony,zerkms/symfony,Triiistan/symfony,gonzalovilaseca/symfony,ogizanagi/symfony,smatyas/symfony,Engerim/symfony,damienalexandre/symfony,oleg-andreyev/symfony,smatyas/symfony,Amo/symfony,apetitpa/symfony,sgehrig/symfony,codeclimate-testing/symfony,kbond/symfony,Deamon/symfony,smatyas/symfony,romaricdrigon/symfony,localheinz/symfony,Taluu/symfony,damienalexandre/symfony,jvasseur/symfony,fabpot/symfony,fabpot/symfony,chalasr/symfony,iltar/symfony,shieldo/symfony,josephdpurcell/symfony,yceruto/symfony,teohhanhui/symfony,mpdude/symfony,zerkms/symfony,tgalopin/symfony,nicolas-grekas/symfony,sroze/symfony,backbone87/symfony,ro0NL/symfony,pyrech/symfony,Nyholm/symfony,tucksaun/symfony,mnapoli/symfony,OskarStark/symfony,Deamon/symfony,codeclimate-testing/symfony,gnat42/symfony,ajgarlag/symfony,xabbuh/symfony,deguif/symfony,hacfi/symfony,oleg-andreyev/symfony,sgehrig/symfony,sgehrig/symfony,MatTheCat/symfony,SaschaDens/symfony,jzawadzki/symfony,paradajozsef/symfony,Triiistan/symfony,garak/symfony,e-moe/symfony,damienalexandre/symfony,sroze/symfony,Einenlum/symfony,e-moe/symfony,curry684/symfony,gonzalovilaseca/symfony,d-ph/symfony,apetitpa/symfony,phramz/symfony,oleg-andreyev/symfony,dmaicher/symfony,pamil/symfony,d-ph/symfony,Pierstoval/symfony,pyrech/symfony,jderusse/symfony,e-moe/symfony,stof/symfony,yceruto/symfony,lyrixx/symfony,Pierstoval/symfony,gimler/symfony,derrabus/symfony,Aliance/symfony,lyrixx/symfony,vincentaubert/symfony,Strate/symfony,aeoris/symfony,ogizanagi/symfony,Taluu/symfony,SpacePossum/symfony,c960657/symfony,Aliance/symfony,1ed/symfony,d-ph/symfony,gimler/symfony,Deamon/symfony,mnapoli/symfony,Koc/symfony,arjenm/symfony,Simperfit/symfony,gencer/symfony,1ed/symfony,iltar/symfony,Strate/symfony,aeoris/symfony,maidmaid/symfony,gnat42/symfony,mnapoli/symfony,docteurklein/symfony,phramz/symfony,bendavies/symfony,shieldo/symfony,hhamon/symfony,pamil/symfony,mnapoli/symfony,OndraM/symfony,jderusse/symfony,mpdude/symfony,MatTheCat/symfony,docteurklein/symfony,Slamdunk/symfony,jakzal/symfony,inso/symfony,SpacePossum/symfony,mweimerskirch/symfony,shieldo/symfony,mihai-stancu/symfony,zcodes/symfony,weaverryan/symfony,chalasr/symfony,hacfi/symfony,iltar/symfony,MatTheCat/symfony,HeahDude/symfony,frankdejonge/symfony,localheinz/symfony,andreia/symfony,gnat42/symfony,pierredup/symfony,stof/symfony,weaverryan/symfony,mpdude/symfony,stof/symfony