Reapply "[Metadata] Preserve MD_prof when merging instructions when one is missing.""#135270

snehasish wants to merge 1 commit intomainllvm/llvm-project:mainfrom

revert-134200-revert-132433-users/snehasish/03-21-_metadata_preserve_md_prof_when_merging_instructions_when_one_is_missingllvm/llvm-project:revert-134200-revert-132433-users/snehasish/03-21-_metadata_preserve_md_prof_when_merging_instructions_when_one_is_missingCopy head branch name to clipboard