[llvm] [Remarks] Introduce tool to count remarks. (PR #66214)

[Aaron Ballman via llvm-commits]

AaronBallman wrote:

There are still broken bots from this change: https://lab.llvm.org/buildbot/#/builders/124/builds/8595 @zjaffal, please revert the changes until you have a fix ready.

https://github.com/llvm/llvm-project/pull/66214