[libc] [clang] [flang] [clang-tools-extra] [llvm] [clang][Sema] Populate function template depth at AddTemplateOverloadCandidate (PR #80395)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

I don't see much value in a backport, particularly since this affects back to Clang 12.  Else, LGTM.

https://github.com/llvm/llvm-project/pull/80395