Alfredo Di Napoli authored Dec 08, 2020 and Marge Bot committed Jan 09, 2021

This commit removes the errShortString field from the ErrMsg type,
allowing us to cleanup a lot of dynflag-dependent error functions, and
move them in a more specialised 'GHC.Driver.Errors' closer to the
driver, where they are actually used.

Metric Increase:
  T4801
  T9961