[clang] [llvm] [Serialization] Use stable hash functions (PR #96136)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

This looks generally good.

> Some check-clang-modules tests still fail (@ChuanqiXu9) 

What does this mean? Do you mean there are some failures after this patch? What are they? Or are these tests failing before this patch?

https://github.com/llvm/llvm-project/pull/96136