[llvm] [Remarks] Emit SROA and mem2reg missed remarks (PR #221094)

[Manasij Mukherjee via llvm-commits]

manasij7479 wrote:

>So a remark pointing at an escape probably isn't telling the user anything they didn't already know, and it's going to drown out useful remarks.
  
@efriedma-quic How about we only emit a remark when we can provide an accurate reason, and drop the blanket 'failed' ones? Would that address your concerns? 

https://github.com/llvm/llvm-project/pull/221094