[clang] [Clang][AST] Introduce `ExplicitInstantiationDecl` to preserve source info and fix diagnostic locations (PR #191658)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov commented:

Well done, thanks!

Just a few nits here, but great work, I appreciate.

https://github.com/llvm/llvm-project/pull/191658