Auto merge of #19282 - CYBAI:use-macro-for-font-variant, r=canaltinova
Auto merge of #19282 - CYBAI:use-macro-for-font-variant, r=canaltinova

Use macro to impl From for font variant

As I discussed in #19277, I'd like to change the implementation for `From` of font variant to use macro, `impl_gecko_keyword_conversions`.
r? @emilio

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes update `From` impl for font variant to use macro `impl_gecko_keyword_conversions`.
- [x] These changes do not require tests

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