[llvm] Constant Fold Logf128 calls (PR #84501)

[Matthew Devereau via llvm-commits]

MDevereau wrote:

> You can write code in lit.cfg.py to add a feature to config.available_features, then check for it using a REQUIRES clause.

I've implemented this and removed the unit tests. Instead I'm now relying on InstSimplify tests.

https://github.com/llvm/llvm-project/pull/84501