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

[Manasij Mukherjee via llvm-commits]

manasij7479 wrote:

@efriedma-quic I agree that we should only emit the diagnostic for a late run. 
     
I want to handle this separately though, not at the point of emission. The pass itself having special purpose code depending on how it is being run makes for a leaky abstraction. 

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