[llvm] [MemProf] Streamline and avoid unnecessary context id duplication (PR #107918)

[Teresa Johnson via llvm-commits]

teresajohnson wrote:

> nit: We should convert the callcontextinfo from a tuple to a struct at some point to make it easier to read the code here without having to refer to the decl.

I agree, I'll prep an nfc patch to do that.

https://github.com/llvm/llvm-project/pull/107918