Detect GHC 9.4 and use -fprof-late

[dpwiz]

For #6197, following https://well-typed.com/blog/2023/03/prof-late/

• Any changes that could be relevant to users have been recorded in ChangeLog.md.
• The documentation has been updated, if necessary
  • The change seems to "do the right thing" without bothering users with details. The profiling just works better.