[sil] Improve comments on macro definitions in SILNodes.def.
[sil] Improve comments on macro definitions in SILNodes.def.

Specifically:

1. The comment for SINGLE_VALUE_INST did not match its actual macro definition
with Parent and TextualName being swapped.
2. I noticed that there were a few macros without any documentation. I added
documentation for them.

hooman/swift,rudkx/swift,parkera/swift,nathawes/swift,benlangmuir/swift,gribozavr/swift,sschiau/swift,nathawes/swift,karwa/swift,gribozavr/swift,shahmishal/swift,parkera/swift,airspeedswift/swift,sschiau/swift,amraboelela/swift,stephentyrone/swift,gregomni/swift,alblue/swift,rudkx/swift,tkremenek/swift,aschwaighofer/swift,shahmishal/swift,gregomni/swift,parkera/swift,CodaFi/swift,alblue/swift,ahoppen/swift,jckarter/swift,JGiola/swift,glessard/swift,nathawes/swift,jmgc/swift,devincoughlin/swift,hooman/swift,CodaFi/swift,danielmartin/swift,austinzheng/swift,xwu/swift,austinzheng/swift,apple/swift,aschwaighofer/swift,ahoppen/swift,allevato/swift,roambotics/swift,benlangmuir/swift,atrick/swift,harlanhaskins/swift,allevato/swift,harlanhaskins/swift,atrick/swift,shahmishal/swift,ahoppen/swift,JGiola/swift,xwu/swift,airspeedswift/swift,JGiola/swift,practicalswift/swift,amraboelela/swift,harlanhaskins/swift,CodaFi/swift,gregomni/swift,parkera/swift,amraboelela/swift,jckarter/swift,allevato/swift,CodaFi/swift,JGiola/swift,karwa/swift,practicalswift/swift,devincoughlin/swift,parkera/swift,nathawes/swift,xwu/swift,atrick/swift,practicalswift/swift,glessard/swift,hooman/swift,shajrawi/swift,lorentey/swift,austinzheng/swift,karwa/swift,devincoughlin/swift,JGiola/swift,roambotics/swift,tkremenek/swift,danielmartin/swift,aschwaighofer/swift,aschwaighofer/swift,rudkx/swift,roambotics/swift,harlanhaskins/swift,shajrawi/swift,airspeedswift/swift,karwa/swift,allevato/swift,danielmartin/swift,tkremenek/swift,lorentey/swift,apple/swift,benlangmuir/swift,glessard/swift,shahmishal/swift,shajrawi/swift,gregomni/swift,gribozavr/swift,xwu/swift,jckarter/swift,tkremenek/swift,shajrawi/swift,atrick/swift,karwa/swift,stephentyrone/swift,stephentyrone/swift,roambotics/swift,lorentey/swift,apple/swift,jmgc/swift,xwu/swift,xedin/swift,sschiau/swift,allevato/swift,aschwaighofer/swift,practicalswift/swift,CodaFi/swift,stephentyrone/swift,gribozavr/swift,alblue/swift,jckarter/swift,allevato/swift,nathawes/swift,danielmartin/swift,gribozavr/swift,danielmartin/swift,xedin/swift,jmgc/swift,lorentey/swift,tkremenek/swift,gribozavr/swift,stephentyrone/swift,ahoppen/swift,CodaFi/swift,rudkx/swift,airspeedswift/swift,sschiau/swift,practicalswift/swift,xedin/swift,xwu/swift,sschiau/swift,danielmartin/swift,tkremenek/swift,harlanhaskins/swift,ahoppen/swift,hooman/swift,xwu/swift,austinzheng/swift,roambotics/swift,harlanhaskins/swift,glessard/swift,devincoughlin/swift,practicalswift/swift,apple/swift,benlangmuir/swift,lorentey/swift,shajrawi/swift,devincoughlin/swift,xedin/swift,xedin/swift,gribozavr/swift,shajrawi/swift,apple/swift,aschwaighofer/swift,devincoughlin/swift,jckarter/swift,parkera/swift,airspeedswift/swift,jmgc/swift,lorentey/swift,hooman/swift,devincoughlin/swift,stephentyrone/swift,tkremenek/swift,jmgc/swift,atrick/swift,austinzheng/swift,devincoughlin/swift,shahmishal/swift,austinzheng/swift,shahmishal/swift,sschiau/swift,jmgc/swift,shahmishal/swift,parkera/swift,gribozavr/swift,alblue/swift,xedin/swift,danielmartin/swift,apple/swift,amraboelela/swift,jckarter/swift,gregomni/swift,sschiau/swift,sschiau/swift,airspeedswift/swift,glessard/swift,xedin/swift,lorentey/swift,benlangmuir/swift,shajrawi/swift,jmgc/swift,austinzheng/swift,CodaFi/swift,gregomni/swift,alblue/swift,atrick/swift,amraboelela/swift,practicalswift/swift,karwa/swift,parkera/swift,shajrawi/swift,alblue/swift,hooman/swift,karwa/swift,ahoppen/swift,amraboelela/swift,glessard/swift,nathawes/swift,stephentyrone/swift,shahmishal/swift,airspeedswift/swift,nathawes/swift,jckarter/swift,harlanhaskins/swift,aschwaighofer/swift,lorentey/swift,amraboelela/swift,rudkx/swift,karwa/swift,hooman/swift,rudkx/swift,practicalswift/swift,JGiola/swift,xedin/swift,roambotics/swift,alblue/swift,benlangmuir/swift,allevato/swift