[llvm] [ADT] Update hash function of uint64_t for DenseMap (PR #95734)

[Chuanqi Xu via llvm-commits]

ChuanqiXu9 wrote:

It looks like there are some discussion about how to implement the hash for DenseMap best in practice. This is great and valuable. But I feel I don't have the capability to handle that. So how about opening this in a separate RFC and in this page, let's try to focus on if the patch itself is good to go? 

https://github.com/llvm/llvm-project/pull/95734