[llvm] [InlineCost] Cache collectEphemeralValues() to save compile time (PR #130210)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

can we make this a proper pass manager analysis and query the analysis manager instead of an inliner-specific cache, just like `GetAssumptionCache`? that way any pass that wants to calculate ephemeral values can do so the same way and potentially reuse it. I believe if we go down this route, we need to invalidate analyses on the callee a bit more aggressively, as in moving [this](https://github.com/llvm/llvm-project/blob/e4a6e2eb7176e677eb9a9c45913a284d374d60c5/llvm/lib/Transforms/IPO/Inliner.cpp#L529) to [here](https://github.com/llvm/llvm-project/blob/e4a6e2eb7176e677eb9a9c45913a284d374d60c5/llvm/lib/Transforms/IPO/Inliner.cpp#L392), in the case we are inlining a recursive call (we probably should already be doing this anyway).

https://github.com/llvm/llvm-project/pull/130210