[Lexer] Performance improvement for Lexer::kindOfIdentifier (#15168)
[Lexer] Performance improvement for Lexer::kindOfIdentifier (#15168)

Don't check SIL_KEYWORDs when we're not in SIL mode.
Lexer::kindOfIdentifier is super hot-path because many of
tokens in a swift source file are keywords or identifiers.
jopamer/swift,lorentey/swift,gribozavr/swift,nathawes/swift,sschiau/swift,hooman/swift,glessard/swift,roambotics/swift,apple/swift,brentdax/swift,gregomni/swift,shajrawi/swift,roambotics/swift,lorentey/swift,gribozavr/swift,CodaFi/swift,devincoughlin/swift,benlangmuir/swift,apple/swift,stephentyrone/swift,airspeedswift/swift,hooman/swift,gregomni/swift,harlanhaskins/swift,huonw/swift,tjw/swift,hooman/swift,gribozavr/swift,CodaFi/swift,xedin/swift,huonw/swift,glessard/swift,brentdax/swift,jckarter/swift,austinzheng/swift,tkremenek/swift,shahmishal/swift,austinzheng/swift,sschiau/swift,tjw/swift,xwu/swift,nathawes/swift,rudkx/swift,aschwaighofer/swift,JGiola/swift,jmgc/swift,harlanhaskins/swift,shahmishal/swift,shahmishal/swift,practicalswift/swift,gribozavr/swift,jopamer/swift,karwa/swift,atrick/swift,atrick/swift,atrick/swift,aschwaighofer/swift,xedin/swift,natecook1000/swift,alblue/swift,hooman/swift,austinzheng/swift,CodaFi/swift,nathawes/swift,atrick/swift,benlangmuir/swift,jmgc/swift,roambotics/swift,airspeedswift/swift,jopamer/swift,gribozavr/swift,lorentey/swift,hooman/swift,allevato/swift,JGiola/swift,karwa/swift,alblue/swift,harlanhaskins/swift,alblue/swift,jopamer/swift,CodaFi/swift,stephentyrone/swift,practicalswift/swift,stephentyrone/swift,nathawes/swift,alblue/swift,allevato/swift,glessard/swift,jmgc/swift,xwu/swift,amraboelela/swift,danielmartin/swift,xwu/swift,devincoughlin/swift,JGiola/swift,danielmartin/swift,xwu/swift,tkremenek/swift,airspeedswift/swift,benlangmuir/swift,huonw/swift,tjw/swift,atrick/swift,atrick/swift,stephentyrone/swift,lorentey/swift,ahoppen/swift,jmgc/swift,xedin/swift,rudkx/swift,glessard/swift,apple/swift,shahmishal/swift,natecook1000/swift,sschiau/swift,nathawes/swift,aschwaighofer/swift,practicalswift/swift,jckarter/swift,brentdax/swift,rudkx/swift,huonw/swift,austinzheng/swift,amraboelela/swift,shahmishal/swift,harlanhaskins/swift,ahoppen/swift,amraboelela/swift,devincoughlin/swift,jmgc/swift,xedin/swift,devincoughlin/swift,amraboelela/swift,austinzheng/swift,shajrawi/swift,sschiau/swift,shahmishal/swift,roambotics/swift,harlanhaskins/swift,allevato/swift,alblue/swift,amraboelela/swift,practicalswift/swift,xedin/swift,stephentyrone/swift,gregomni/swift,shahmishal/swift,tjw/swift,glessard/swift,natecook1000/swift,gregomni/swift,tkremenek/swift,shajrawi/swift,shajrawi/swift,airspeedswift/swift,sschiau/swift,devincoughlin/swift,practicalswift/swift,devincoughlin/swift,jmgc/swift,shajrawi/swift,devincoughlin/swift,karwa/swift,benlangmuir/swift,alblue/swift,jmgc/swift,natecook1000/swift,roambotics/swift,parkera/swift,shajrawi/swift,jopamer/swift,huonw/swift,huonw/swift,huonw/swift,aschwaighofer/swift,gregomni/swift,benlangmuir/swift,gribozavr/swift,sschiau/swift,CodaFi/swift,danielmartin/swift,aschwaighofer/swift,aschwaighofer/swift,roambotics/swift,danielmartin/swift,gribozavr/swift,airspeedswift/swift,nathawes/swift,jopamer/swift,hooman/swift,ahoppen/swift,practicalswift/swift,parkera/swift,CodaFi/swift,natecook1000/swift,karwa/swift,glessard/swift,sschiau/swift,jckarter/swift,xwu/swift,ahoppen/swift,amraboelela/swift,apple/swift,karwa/swift,JGiola/swift,harlanhaskins/swift,practicalswift/swift,tkremenek/swift,lorentey/swift,ahoppen/swift,lorentey/swift,shahmishal/swift,parkera/swift,amraboelela/swift,alblue/swift,xwu/swift,practicalswift/swift,stephentyrone/swift,jckarter/swift,natecook1000/swift,ahoppen/swift,xwu/swift,karwa/swift,nathawes/swift,shajrawi/swift,natecook1000/swift,JGiola/swift,brentdax/swift,aschwaighofer/swift,lorentey/swift,shajrawi/swift,tkremenek/swift,brentdax/swift,karwa/swift,stephentyrone/swift,allevato/swift,jopamer/swift,devincoughlin/swift,harlanhaskins/swift,austinzheng/swift,austinzheng/swift,jckarter/swift,allevato/swift,danielmartin/swift,benlangmuir/swift,xedin/swift,xedin/swift,parkera/swift,gregomni/swift,danielmartin/swift,parkera/swift,rudkx/swift,xedin/swift,danielmartin/swift,CodaFi/swift,parkera/swift,apple/swift,jckarter/swift,tjw/swift,airspeedswift/swift,gribozavr/swift,lorentey/swift,rudkx/swift,brentdax/swift,allevato/swift,rudkx/swift,tjw/swift,brentdax/swift,jckarter/swift,karwa/swift,tjw/swift,apple/swift,tkremenek/swift,tkremenek/swift,allevato/swift,airspeedswift/swift,parkera/swift,hooman/swift,parkera/swift,sschiau/swift,JGiola/swift