[clang] [clang] check constant template parameters in dependent contexts (PR #159463)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

> I think this makes sense, it seems to do as described at least. I'm not sure WHAT, but it feels like we could/should do a better job with some demonstrative tests though.

I am open to suggestions, I can't think of anything which would demonstrate this better or show some interesting corner case not shown in the current test changes already.

https://github.com/llvm/llvm-project/pull/159463