[clang] [clang][Sema] Don't mark VarDecls of bindings in tuple-like decompositions as implicit (PR #100355)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

CC @zygoloid for design opinions.

This holding variable is really weird in that it's both not spelled in source (the user doesn't give it a name) but is spelled in source (only exists because of a source construct). I think that makes it hard to know whether it should or should not be marked as implicit.

https://github.com/llvm/llvm-project/pull/100355