[clang] [Clang][Sema] fix crash in codegen stage when an lambda expression declared in an unevaluated context (PR #80802)

[Qizhi Hu via cfe-commits]

jcsxky wrote:

@cor3ntin @erichkeane Could you please take another look at this PR? I think current version would be a reasonable fix since it transforms type only when it's needed. Or you have any other opinions? Thank you for guidance!

https://github.com/llvm/llvm-project/pull/80802