[lld] [lld-macho,BalancedPartition] Simplify relocation hash and avoid xxHash (PR #121729)

[Ellis Hoag via llvm-commits]

ellishg wrote:

> > > @ellishg Does the current PR look good to you?
> > 
> > 
> > Can we use only `xxh3_64bits()` in this PR for simplicity and flexibility?
> 
> Do you want two PRs, one changing xxHash64 to `xxh3_64bits`, and the other simplifying the relocation hash?
> 
> If this is your intention, I can pre-land one commit to make just the xxHash64 change, and rebase this PR.

One PR should be ok. I was just saying we should use `xxh3_64bits()` instead of `read32le()` on line 100.

https://github.com/llvm/llvm-project/pull/121729