[Sema] DebuggerTestingTransform: avoid re-using AST nodes in generated code
[Sema] DebuggerTestingTransform: avoid re-using AST nodes in generated code

While building a closure to inject `checkExpect` code, clone member
references associated with assignment. Re-using AST nodes is generally
invalid. This is visible with multi-statement closure inference enabled,
because the body is type-checked together with enclosing context
and both elements end up sharing `DeclRefExpr` and `MemberRefExpr`s.

ahoppen/swift,rudkx/swift,atrick/swift,roambotics/swift,JGiola/swift,ahoppen/swift,apple/swift,glessard/swift,ahoppen/swift,rudkx/swift,glessard/swift,rudkx/swift,ahoppen/swift,ahoppen/swift,benlangmuir/swift,rudkx/swift,glessard/swift,ahoppen/swift,atrick/swift,apple/swift,glessard/swift,benlangmuir/swift,gregomni/swift,apple/swift,rudkx/swift,gregomni/swift,JGiola/swift,gregomni/swift,rudkx/swift,benlangmuir/swift,roambotics/swift,roambotics/swift,roambotics/swift,JGiola/swift,benlangmuir/swift,glessard/swift,JGiola/swift,apple/swift,apple/swift,atrick/swift,atrick/swift,glessard/swift,benlangmuir/swift,gregomni/swift,roambotics/swift,apple/swift,gregomni/swift,gregomni/swift,atrick/swift,JGiola/swift,benlangmuir/swift,atrick/swift,roambotics/swift,JGiola/swift