Proposal: Don't read environment files by default

Hi all, Environment files have caused a large amount of pain for users because they are read by default by GHC. For example: https://github.com/haskell/cabal/issues/4542 Cabal developers have indicated that they are not going to stop generating them by default despite the overwhelming user pressure. Therefore I propose that users should opt-in to using environment files by having to explicitly pass a flag to enable the search behavior. This will provide a much better user experience overall and will stop tooling having to isolate itself from their existence. Cheers, Matt