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

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks approved this pull request.

I actually think the unittest is completely unnecessary, it's basically just checking that the analysis manager/invalidation works, which should be covered by other tests

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