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

[Shubham Sandeep Rastogi via llvm-commits]

rastogishubham wrote:

The dropped statistics for the updated patch are:

AlwaysInlinerPass, 2
SCCPPass, 6
InstCombinePass, 19
EliminateAvailableExternallyPass, 64
SimplifyCFGPass, 157
GlobalOptPass, 192
JumpThreadingPass, 439
ADCEPass, 5536

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