[llvm] [Code Coverage] Add a tool to check test coverage of a patch (PR #71841)

[Shivam Gupta via llvm-commits]

xgupta wrote:

Actually, added a few reviewers who are contributing to LLVM Python code, just to make sure it is following the correct coding practices. I haven't worked on Python before this.

https://github.com/llvm/llvm-project/pull/71841