[clang] don't create type source info for vardecl created for structured bindings (#153923)
These are implicit vardecls which its type was never written in source
code. Don't create a TypeLoc and give it a fake source location.
The fake as-written type also didn't match the actual type, which after
fixing this gives some unrelated test churn on a CFG dump, since
statement printing prefers type source info if thats available.
Fixes https://github.com/llvm/llvm-project/issues/153649
This is a regression introduced in
https://github.com/llvm/llvm-project/pull/147835
This regression was never released, so no release notes are added.