[Integer protocols] Make .negate() the customization point (#4413)
[Integer protocols] Make .negate() the customization point (#4413)

The SignedArithmetic protocol provides default implementations for both
negate() and negated(), with negate() calling negated(). This is inconsistent
with the Arithmetic protocol, which provides implementations of the nonmutating
methods that call their mutating counterparts. This flips the implementations
of negate() and negated() so an implementer only has to focus on mutating
methods.
arvedviehweger/swift,gribozavr/swift,shajrawi/swift,tkremenek/swift,glessard/swift,uasys/swift,glessard/swift,amraboelela/swift,shahmishal/swift,alblue/swift,austinzheng/swift,harlanhaskins/swift,uasys/swift,rudkx/swift,jtbandes/swift,return/swift,zisko/swift,natecook1000/swift,jtbandes/swift,tjw/swift,deyton/swift,devincoughlin/swift,jckarter/swift,gribozavr/swift,milseman/swift,apple/swift,nathawes/swift,calebd/swift,nathawes/swift,glessard/swift,jmgc/swift,practicalswift/swift,sschiau/swift,return/swift,alblue/swift,sschiau/swift,frootloops/swift,aschwaighofer/swift,Jnosh/swift,parkera/swift,deyton/swift,djwbrown/swift,roambotics/swift,gregomni/swift,xwu/swift,return/swift,lorentey/swift,huonw/swift,shajrawi/swift,uasys/swift,austinzheng/swift,atrick/swift,sschiau/swift,alblue/swift,deyton/swift,stephentyrone/swift,shajrawi/swift,swiftix/swift,parkera/swift,deyton/swift,jtbandes/swift,uasys/swift,karwa/swift,karwa/swift,JGiola/swift,benlangmuir/swift,harlanhaskins/swift,devincoughlin/swift,aschwaighofer/swift,austinzheng/swift,parkera/swift,brentdax/swift,xwu/swift,gribozavr/swift,allevato/swift,OscarSwanros/swift,gribozavr/swift,xedin/swift,harlanhaskins/swift,devincoughlin/swift,swiftix/swift,danielmartin/swift,zisko/swift,jmgc/swift,milseman/swift,xedin/swift,OscarSwanros/swift,Jnosh/swift,calebd/swift,nathawes/swift,glessard/swift,jopamer/swift,airspeedswift/swift,ahoppen/swift,karwa/swift,xedin/swift,frootloops/swift,return/swift,karwa/swift,lorentey/swift,rudkx/swift,frootloops/swift,tjw/swift,apple/swift,lorentey/swift,parkera/swift,alblue/swift,karwa/swift,hooman/swift,tjw/swift,return/swift,calebd/swift,airspeedswift/swift,natecook1000/swift,gregomni/swift,shahmishal/swift,swiftix/swift,djwbrown/swift,benlangmuir/swift,austinzheng/swift,arvedviehweger/swift,harlanhaskins/swift,hughbe/swift,hooman/swift,jckarter/swift,hooman/swift,JGiola/swift,gregomni/swift,uasys/swift,benlangmuir/swift,roambotics/swift,rudkx/swift,xwu/swift,milseman/swift,shajrawi/swift,CodaFi/swift,tkremenek/swift,amraboelela/swift,gribozavr/swift,frootloops/swift,djwbrown/swift,swiftix/swift,stephentyrone/swift,shajrawi/swift,benlangmuir/swift,jckarter/swift,tkremenek/swift,amraboelela/swift,jopamer/swift,xedin/swift,karwa/swift,jckarter/swift,calebd/swift,jtbandes/swift,practicalswift/swift,allevato/swift,shajrawi/swift,rudkx/swift,allevato/swift,huonw/swift,xwu/swift,CodaFi/swift,xedin/swift,CodaFi/swift,shahmishal/swift,sschiau/swift,jmgc/swift,frootloops/swift,lorentey/swift,jopamer/swift,natecook1000/swift,danielmartin/swift,ahoppen/swift,shahmishal/swift,apple/swift,arvedviehweger/swift,parkera/swift,danielmartin/swift,jopamer/swift,devincoughlin/swift,hooman/swift,brentdax/swift,zisko/swift,natecook1000/swift,huonw/swift,jopamer/swift,tjw/swift,amraboelela/swift,devincoughlin/swift,Jnosh/swift,harlanhaskins/swift,natecook1000/swift,apple/swift,hughbe/swift,felix91gr/swift,frootloops/swift,xedin/swift,hooman/swift,huonw/swift,practicalswift/swift,sschiau/swift,felix91gr/swift,sschiau/swift,practicalswift/swift,danielmartin/swift,rudkx/swift,allevato/swift,JGiola/swift,benlangmuir/swift,brentdax/swift,felix91gr/swift,roambotics/swift,gribozavr/swift,CodaFi/swift,jmgc/swift,aschwaighofer/swift,atrick/swift,uasys/swift,roambotics/swift,airspeedswift/swift,jopamer/swift,lorentey/swift,lorentey/swift,hughbe/swift,rudkx/swift,stephentyrone/swift,atrick/swift,stephentyrone/swift,JGiola/swift,gregomni/swift,aschwaighofer/swift,deyton/swift,austinzheng/swift,practicalswift/swift,djwbrown/swift,apple/swift,felix91gr/swift,arvedviehweger/swift,nathawes/swift,huonw/swift,allevato/swift,amraboelela/swift,harlanhaskins/swift,stephentyrone/swift,danielmartin/swift,alblue/swift,hughbe/swift,harlanhaskins/swift,ahoppen/swift,tkremenek/swift,amraboelela/swift,return/swift,milseman/swift,alblue/swift,jtbandes/swift,practicalswift/swift,felix91gr/swift,milseman/swift,lorentey/swift,milseman/swift,benlangmuir/swift,austinzheng/swift,jmgc/swift,OscarSwanros/swift,nathawes/swift,brentdax/swift,calebd/swift,xedin/swift,parkera/swift,jckarter/swift,gregomni/swift,xwu/swift,jopamer/swift,jmgc/swift,shajrawi/swift,return/swift,huonw/swift,zisko/swift,djwbrown/swift,alblue/swift,hooman/swift,practicalswift/swift,jtbandes/swift,xedin/swift,djwbrown/swift,calebd/swift,hughbe/swift,arvedviehweger/swift,ahoppen/swift,shahmishal/swift,glessard/swift,parkera/swift,danielmartin/swift,tkremenek/swift,deyton/swift,swiftix/swift,calebd/swift,arvedviehweger/swift,apple/swift,stephentyrone/swift,gribozavr/swift,stephentyrone/swift,OscarSwanros/swift,aschwaighofer/swift,OscarSwanros/swift,nathawes/swift,devincoughlin/swift,brentdax/swift,hughbe/swift,zisko/swift,ahoppen/swift,swiftix/swift,shajrawi/swift,hughbe/swift,CodaFi/swift,devincoughlin/swift,Jnosh/swift,jckarter/swift,uasys/swift,parkera/swift,tkremenek/swift,djwbrown/swift,tjw/swift,tjw/swift,airspeedswift/swift,natecook1000/swift,practicalswift/swift,airspeedswift/swift,milseman/swift,karwa/swift,Cod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