script: Call content_and_heritage_changed from children_changed instead of add_child / remove_child.
script: Call content_and_heritage_changed from children_changed instead of add_child / remove_child.

add_child / remove_child aren't called when a node character data changed. This
is important for finer grained invalidation.

The only test that tests this is now wallpapered, but won't be after #19164.

szeged/servo,saneyuki/servo,peterjoel/servo,sadmansk/servo,mattnenterprise/servo,SimonSapin/servo,DominoTree/servo,saneyuki/servo,pyfisch/servo,eddyb/servo,ConnorGBrewster/servo,CJ8664/servo,upsuper/servo,dsandeephegde/servo,notriddle/servo,DominoTree/servo,saneyuki/servo,emilio/servo,eddyb/servo,jimberlage/servo,jimberlage/servo,pyfisch/servo,pyfisch/servo,nnethercote/servo,peterjoel/servo,paulrouget/servo,CJ8664/servo,szeged/servo,mattnenterprise/servo,cbrewster/servo,mattnenterprise/servo,CJ8664/servo,dsandeephegde/servo,larsbergstrom/servo,cbrewster/servo,avadacatavra/servo,splav/servo,dsandeephegde/servo,CJ8664/servo,emilio/servo,KiChjang/servo,emilio/servo,larsbergstrom/servo,splav/servo,ConnorGBrewster/servo,notriddle/servo,saneyuki/servo,emilio/servo,emilio/servo,emilio/servo,rnestler/servo,larsbergstrom/servo,paulrouget/servo,KiChjang/servo,dati91/servo,thiagopnts/servo,dsandeephegde/servo,canaltinova/servo,cbrewster/servo,nnethercote/servo,paulrouget/servo,sadmansk/servo,KiChjang/servo,upsuper/servo,dati91/servo,szeged/servo,notriddle/servo,thiagopnts/servo,dsandeephegde/servo,avadacatavra/servo,CJ8664/servo,eddyb/servo,rnestler/servo,DominoTree/servo,SimonSapin/servo,pyfisch/servo,DominoTree/servo,eddyb/servo,eddyb/servo,peterjoel/servo,nnethercote/servo,notriddle/servo,paulrouget/servo,dsandeephegde/servo,canaltinova/servo,thiagopnts/servo,jimberlage/servo,fiji-flo/servo,KiChjang/servo,jimberlage/servo,notriddle/servo,mbrubeck/servo,eddyb/servo,fiji-flo/servo,ConnorGBrewster/servo,larsbergstrom/servo,canaltinova/servo,paulrouget/servo,canaltinova/servo,canaltinova/servo,upsuper/servo,dsandeephegde/servo,CJ8664/servo,anthgur/servo,larsbergstrom/servo,SimonSapin/servo,larsbergstrom/servo,dati91/servo,paulrouget/servo,mbrubeck/servo,KiChjang/servo,mbrubeck/servo,jimberlage/servo,nnethercote/servo,splav/servo,dati91/servo,SimonSapin/servo,thiagopnts/servo,eddyb/servo,szeged/servo,upsuper/servo,splav/servo,CJ8664/servo,szeged/servo,cbrewster/servo,ConnorGBrewster/servo,SimonSapin/servo,szeged/servo,mattnenterprise/servo,thiagopnts/servo,cbrewster/servo,fiji-flo/servo,anthgur/servo,paulrouget/servo,avadacatavra/servo,peterjoel/servo,dati91/servo,cbrewster/servo,anthgur/servo,upsuper/servo,notriddle/servo,jimberlage/servo,DominoTree/servo,splav/servo,splav/servo,mbrubeck/servo,paulrouget/servo,eddyb/servo,canaltinova/servo,avadacatavra/servo,peterjoel/servo,szeged/servo,fiji-flo/servo,SimonSapin/servo,canaltinova/servo,emilio/servo,mbrubeck/servo,splav/servo,KiChjang/servo,KiChjang/servo,larsbergstrom/servo,saneyuki/servo,rnestler/servo,paulrouget/servo,thiagopnts/servo,jimberlage/servo,notriddle/servo,szeged/servo,fiji-flo/servo,peterjoel/servo,cbrewster/servo,mattnenterprise/servo,peterjoel/servo,cbrewster/servo,anthgur/servo,pyfisch/servo,dati91/servo,saneyuki/servo,saneyuki/servo,dati91/servo,notriddle/servo,DominoTree/servo,saneyuki/servo,DominoTree/servo,mattnenterprise/servo,paulrouget/servo,canaltinova/servo,fiji-flo/servo,upsuper/servo,KiChjang/servo,ConnorGBrewster/servo,pyfisch/servo,avadacatavra/servo,saneyuki/servo,ConnorGBrewster/servo,DominoTree/servo,nnethercote/servo,nnethercote/servo,larsbergstrom/servo,notriddle/servo,sadmansk/servo,larsbergstrom/servo,SimonSapin/servo,SimonSapin/servo,fiji-flo/servo,avadacatavra/servo,nnethercote/servo,rnestler/servo,splav/servo,emilio/servo,sadmansk/servo,mattnenterprise/servo,upsuper/servo,DominoTree/servo,mattnenterprise/servo,mbrubeck/servo,rnestler/servo,szeged/servo,nnethercote/servo,anthgur/servo,avadacatavra/servo,splav/servo,notriddle/servo,nnethercote/servo,mbrubeck/servo,rnestler/servo,fiji-flo/servo,sadmansk/servo,KiChjang/servo,pyfisch/servo,peterjoel/servo,peterjoel/servo,pyfisch/servo,anthgur/servo,sadmansk/servo,rnestler/servo,szeged/servo,CJ8664/servo,emilio/servo,splav/servo,ConnorGBrewster/servo,rnestler/servo,anthgur/servo,thiagopnts/servo,pyfisch/servo,avadacatavra/servo,sadmansk/servo,dsandeephegde/servo,larsbergstrom/servo,upsuper/servo,saneyuki/servo,anthgur/servo,thiagopnts/servo,nnethercote/servo,dati91/servo,KiChjang/servo,ConnorGBrewster/servo,sadmansk/servo,pyfisch/servo,emilio/servo,DominoTree/servo,peterjoel/servo,jimberlage/servo,mbrubeck/servo,jimberlage/servo