[clang] [CIR] Start printing/parsing func 'attributes' (PR #169674)

[Henrich Lauko via cfe-commits]

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

Cool, this looks reasonable :) FYI I started cleaning this up in incubator: https://github.com/llvm/clangir/pull/2028

Moving away from extra_attrs  a putting them explicitly on the function. Eventually I hope we will be able to use assembly form direcly which will even for your case here be just `attr-dict-with-keyword`​ and the rest should happen automatically.

https://github.com/llvm/llvm-project/pull/169674