composebox_typeahead: Refactor @mentions logic to not block #streams.
composebox_typeahead: Refactor @mentions logic to not block #streams.

blaze225/zulip,rishig/zulip,andersk/zulip,vabs22/zulip,susansls/zulip,isht3/zulip,jainayush975/zulip,susansls/zulip,hackerkid/zulip,punchagan/zulip,Galexrt/zulip,arpith/zulip,KingxBanana/zulip,zacps/zulip,showell/zulip,vikas-parashar/zulip,brockwhittaker/zulip,jainayush975/zulip,blaze225/zulip,timabbott/zulip,rishig/zulip,reyha/zulip,jainayush975/zulip,paxapy/zulip,reyha/zulip,rht/zulip,cosmicAsymmetry/zulip,arpith/zulip,synicalsyntax/zulip,brainwane/zulip,sharmaeklavya2/zulip,dhcrzf/zulip,j831/zulip,niftynei/zulip,vaidap/zulip,joyhchen/zulip,cosmicAsymmetry/zulip,eeshangarg/zulip,isht3/zulip,joyhchen/zulip,amyliu345/zulip,j831/zulip,TigorC/zulip,christi3k/zulip,dattatreya303/zulip,TigorC/zulip,vaidap/zulip,PhilSk/zulip,Galexrt/zulip,SmartPeople/zulip,Juanvulcano/zulip,zacps/zulip,Diptanshu8/zulip,joyhchen/zulip,eeshangarg/zulip,jainayush975/zulip,arpith/zulip,christi3k/zulip,sharmaeklavya2/zulip,reyha/zulip,tommyip/zulip,tommyip/zulip,mahim97/zulip,amyliu345/zulip,christi3k/zulip,ryanbackman/zulip,Jianchun1/zulip,amyliu345/zulip,Galexrt/zulip,eeshangarg/zulip,verma-varsha/zulip,amanharitsh123/zulip,AZtheAsian/zulip,shubhamdhama/zulip,niftynei/zulip,AZtheAsian/zulip,vaidap/zulip,arpith/zulip,jackrzhang/zulip,dawran6/zulip,timabbott/zulip,sonali0901/zulip,Juanvulcano/zulip,hackerkid/zulip,jphilipsen05/zulip,mahim97/zulip,paxapy/zulip,hackerkid/zulip,mahim97/zulip,isht3/zulip,Juanvulcano/zulip,souravbadami/zulip,souravbadami/zulip,joyhchen/zulip,samatdav/zulip,samatdav/zulip,zulip/zulip,cosmicAsymmetry/zulip,joyhchen/zulip,Galexrt/zulip,shubhamdhama/zulip,eeshangarg/zulip,kou/zulip,niftynei/zulip,brockwhittaker/zulip,KingxBanana/zulip,brockwhittaker/zulip,punchagan/zulip,SmartPeople/zulip,blaze225/zulip,isht3/zulip,aakash-cr7/zulip,PhilSk/zulip,showell/zulip,zacps/zulip,vaidap/zulip,KingxBanana/zulip,calvinleenyc/zulip,sonali0901/zulip,hackerkid/zulip,mahim97/zulip,paxapy/zulip,Galexrt/zulip,ryanbackman/zulip,kou/zulip,vabs22/zulip,Jianchun1/zulip,samatdav/zulip,brainwane/zulip,vikas-parashar/zulip,jackrzhang/zulip,amanharitsh123/zulip,Juanvulcano/zulip,rht/zulip,TigorC/zulip,amanharitsh123/zulip,peguin40/zulip,kou/zulip,zulip/zulip,jrowan/zulip,vabs22/zulip,shubhamdhama/zulip,samatdav/zulip,rishig/zulip,jackrzhang/zulip,showell/zulip,ryanbackman/zulip,paxapy/zulip,TigorC/zulip,rishig/zulip,vabs22/zulip,kou/zulip,calvinleenyc/zulip,rishig/zulip,aakash-cr7/zulip,j831/zulip,verma-varsha/zulip,vikas-parashar/zulip,reyha/zulip,zacps/zulip,zulip/zulip,dhcrzf/zulip,punchagan/zulip,Galexrt/zulip,synicalsyntax/zulip,samatdav/zulip,calvinleenyc/zulip,zulip/zulip,sharmaeklavya2/zulip,rht/zulip,dattatreya303/zulip,eeshangarg/zulip,grave-w-grave/zulip,jackrzhang/zulip,synicalsyntax/zulip,eeshangarg/zulip,jainayush975/zulip,jphilipsen05/zulip,JPJPJPOPOP/zulip,amanharitsh123/zulip,ryanbackman/zulip,shubhamdhama/zulip,vaidap/zulip,punchagan/zulip,SmartPeople/zulip,amanharitsh123/zulip,mahim97/zulip,Jianchun1/zulip,dhcrzf/zulip,andersk/zulip,ryanbackman/zulip,grave-w-grave/zulip,joyhchen/zulip,grave-w-grave/zulip,dhcrzf/zulip,synicalsyntax/zulip,andersk/zulip,Juanvulcano/zulip,rht/zulip,showell/zulip,peguin40/zulip,paxapy/zulip,peguin40/zulip,souravbadami/zulip,zacps/zulip,blaze225/zulip,JPJPJPOPOP/zulip,andersk/zulip,verma-varsha/zulip,PhilSk/zulip,jackrzhang/zulip,synicalsyntax/zulip,sonali0901/zulip,reyha/zulip,amanharitsh123/zulip,vabs22/zulip,JPJPJPOPOP/zulip,synicalsyntax/zulip,sharmaeklavya2/zulip,niftynei/zulip,isht3/zulip,dattatreya303/zulip,showell/zulip,grave-w-grave/zulip,aakash-cr7/zulip,JPJPJPOPOP/zulip,timabbott/zulip,isht3/zulip,vabs22/zulip,mahim97/zulip,blaze225/zulip,PhilSk/zulip,j831/zulip,peguin40/zulip,andersk/zulip,JPJPJPOPOP/zulip,aakash-cr7/zulip,showell/zulip,SmartPeople/zulip,jrowan/zulip,verma-varsha/zulip,dhcrzf/zulip,tommyip/zulip,Juanvulcano/zulip,souravbadami/zulip,calvinleenyc/zulip,susansls/zulip,shubhamdhama/zulip,AZtheAsian/zulip,andersk/zulip,niftynei/zulip,AZtheAsian/zulip,TigorC/zulip,peguin40/zulip,amyliu345/zulip,vikas-parashar/zulip,Jianchun1/zulip,dawran6/zulip,shubhamdhama/zulip,ryanbackman/zulip,paxapy/zulip,synicalsyntax/zulip,kou/zulip,samatdav/zulip,christi3k/zulip,jphilipsen05/zulip,timabbott/zulip,rishig/zulip,christi3k/zulip,jphilipsen05/zulip,punchagan/zulip,zacps/zulip,brockwhittaker/zulip,Diptanshu8/zulip,timabbott/zulip,tommyip/zulip,reyha/zulip,rht/zulip,jainayush975/zulip,Diptanshu8/zulip,grave-w-grave/zulip,Diptanshu8/zulip,PhilSk/zulip,susansls/zulip,dawran6/zulip,Diptanshu8/zulip,kou/zulip,arpith/zulip,PhilSk/zulip,vikas-parashar/zulip,jackrzhang/zulip,SmartPeople/zulip,AZtheAsian/zulip,dattatreya303/zulip,christi3k/zulip,eeshangarg/zulip,sonali0901/zulip,tommyip/zulip,hackerkid/zulip,cosmicAsymmetry/zulip,dhcrzf/zulip,brainwane/zulip,brockwhittaker/zulip,timabbott/zulip,susansls/zulip,dawran6/zulip,calvinleenyc/zulip,brainwane/zulip,sharmaeklavya2/zulip,brockwhittaker/zulip,brainwane/zulip,jrowan/zulip,j831/zulip,dattatreya303/zulip,brainwane/zulip,calvinleenyc/zulip,Jianchun1/zulip,cosmicAsymmetry/zulip,rht/zulip,Diptanshu8/zulip,KingxBanana/zulip,jrowan/zulip,niftynei/zulip,jphilipsen05/zulip,TigorC/zulip,cosmicAsymmetry/zulip,JPJPJPOPOP/zulip,peguin40/zulip,amyliu345/zulip,Jianchun1/zulip,sonali0901/zulip,tommyip/zulip,punchagan/zulip,shubhamdhama/zulip,tommyip/zulip,KingxBanana/zulip,souravbadami/zulip,aakash-cr7/zulip,brainwane/zulip,vaidap/zulip,souravbadami/zulip,punchagan/zulip,jackrzhang/zulip,aakash-cr7/zulip,jrowan/zulip,rht/zulip,j831/zulip,rishig/zulip,dawran6/zulip,blaze225/zulip,andersk/zulip,zulip/zulip,grave-w-grave/zulip,sharmaeklavya2/zulip,verma-varsha/zulip,dattatreya303/zulip,jphilipsen05/zulip,kou/zulip,dawran6/zulip,zulip/zulip,susansls/zulip,timabbott/zulip,jrowan/zulip,KingxBanana/zulip,arpith/zulip,showell/zulip,Galexrt/zulip,verma-varsha/zulip,amyliu345/zulip,hackerkid/zulip,hackerkid/zulip,zulip/zulip,dhcrzf/zulip,sonali0901/zulip,vikas-parashar/zulip,AZtheAsian/zulip,SmartPeople/zulip