[clang] [Sema] Add -Wc++11-narrowing-const-reference (PR #76094)

[Nico Weber via cfe-commits]

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

Thanks! I'm going to merge this since it'll unblock quite a few people. I have a minor comment below that can be addressed in a follow-up.

https://github.com/llvm/llvm-project/pull/76094