[Serialization] Use getAllMembers() to eliminate nondeterminism.
[Serialization] Use getAllMembers() to eliminate nondeterminism.

When serializing the members of a nominal type or extension, use
`getAllMembers()` instead of `getMembers()` to provide a deterministic
ordering.

Fixes rdar://63294687.

JGiola/swift,apple/swift,glessard/swift,apple/swift,xwu/swift,gregomni/swift,benlangmuir/swift,xwu/swift,gregomni/swift,tkremenek/swift,rudkx/swift,tkremenek/swift,hooman/swift,benlangmuir/swift,apple/swift,atrick/swift,roambotics/swift,hooman/swift,hooman/swift,ahoppen/swift,JGiola/swift,parkera/swift,roambotics/swift,benlangmuir/swift,ahoppen/swift,roambotics/swift,atrick/swift,parkera/swift,hooman/swift,ahoppen/swift,gregomni/swift,parkera/swift,gregomni/swift,tkremenek/swift,parkera/swift,rudkx/swift,parkera/swift,apple/swift,apple/swift,atrick/swift,xwu/swift,apple/swift,JGiola/swift,glessard/swift,rudkx/swift,glessard/swift,glessard/swift,xwu/swift,parkera/swift,roambotics/swift,hooman/swift,hooman/swift,xwu/swift,benlangmuir/swift,roambotics/swift,benlangmuir/swift,roambotics/swift,xwu/swift,benlangmuir/swift,tkremenek/swift,gregomni/swift,tkremenek/swift,ahoppen/swift,glessard/swift,atrick/swift,JGiola/swift,rudkx/swift,glessard/swift,parkera/swift,atrick/swift,gregomni/swift,xwu/swift,atrick/swift,JGiola/swift,ahoppen/swift,parkera/swift,tkremenek/swift,hooman/swift,rudkx/swift,JGiola/swift,tkremenek/swift,rudkx/swift,ahoppen/swift