Auto merge of #14645 - upsuper:gecko-builtin-counter-styles, r=heycam
Auto merge of #14645 - upsuper:gecko-builtin-counter-styles, r=heycam

Move {lower,upper}-alpha to extra_servo_values

These two counter styles are supported via @counter-style rules in UA style sheet in Gecko.

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/14645)
<!-- Reviewable:end -->

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