[clang] [Clang][Sema] fix a bug on constraint check with template friend function (PR #90646)

[Qizhi Hu via cfe-commits]

jcsxky wrote:

> I agree with @sdkrystian, even though the test crashes for maybe yet another reason, it demonstrates you can friend a function from a different template context, so comparing the depths from different branches is not helpful.

@mizvekov I missed the case which friend function is declared in an inner class, and [3d27f11](https://github.com/llvm/llvm-project/pull/90646/commits/3d27f11d79b00608bf9135bcc4b4cb859027933a) demonstrates the comparison works fine.

https://github.com/llvm/llvm-project/pull/90646