[llvm] Metrics Pass - Counts different types of instructions in IR (PR #171194)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

using InstCount makes sense, and adding it to the opt pipeline when stats are turned on would be nice, similar to https://github.com/llvm/llvm-project/blob/786498b2816368b02f51514e71f6c6f6ceceba1a/llvm/lib/Passes/PassBuilderPipelines.cpp#L449

https://github.com/llvm/llvm-project/pull/171194