[clang] [Clang][Sema] Warn when 'exclude_from_explicit_instantiation' attribute is used on local classes and members thereof (PR #88777)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

Needs a release note, probably int he 'potentially breaking changes' section? 

https://github.com/llvm/llvm-project/pull/88777