[clang] [Sema] Suggest missing format attributes (PR #166738)

[Vladimir Vuksanovic via cfe-commits]

vvuksanovic wrote:

Thank you for the review, I think all comments are now addressed.

Do you think it would be better to disable checking for missing attributes in the existing `format-strings` tests and instead create a separate test that uses `-Wformat-nonliteral` both with and without `-Wmissing-format-attribute` to compare them?

https://github.com/llvm/llvm-project/pull/166738