[llvm] [Analysis][EphemeralValuesAnalysis][NFCI] Remove EphemeralValuesCache class (PR #132454)

[via llvm-commits]

vporpo wrote:

I agree the unittest is not super useful anymore, but it's a sanity check that the EphemeralValuesAnalysis does return the expected values i.e., they get collected by `run()`. Checking the result after invalidation is pretty much redundant, I will drop it.

https://github.com/llvm/llvm-project/pull/132454