[llvm] [InstrRef] Preserve debug instr num in aarch64-ldst-opt. (PR #136009)

[Shubham Sandeep Rastogi via llvm-commits]

rastogishubham wrote:

@jmorse I hope this looks better? 
@felipepiovezan @adrian-prantl I added a commit to show the changes made from the original patch, for easier review-ability. I will squash them both into one patch before upstreaming.

https://github.com/llvm/llvm-project/pull/136009