[llvm] Add a pass to collect dropped variable statistics (PR #102233)

[Shubham Sandeep Rastogi via llvm-commits]

rastogishubham wrote:

@jmorse Thanks for the feedback! I added a testcase to make sure we don't report dropped variables in a pass like the verifier pass.

I also didn't think of using the DILocalVarible, it was an oversight, I have updated the patch with your feedback!

https://github.com/llvm/llvm-project/pull/102233