cabal check: add command line option to disable some warnings

[ffaf1]

With #8361 soon to be merged, cabal check will warn about missing upper bounds in all dependencies.
As suggested in the discussion, a way to disable this — or disable any specific warning, like hlint does — could be appreciated by some users.

[ffaf1]

Borrowing some ideas from hlint. The UI is simple enough:

  -o --only=HINT                           Specify which hints explicitly
  -i --ignore=HINT                         Ignore a particular hint

HINT is a string prepended to every suggestion:

Cabal/src/Distribution/PackageDescription/Check.hs:1806:8-59: Suggestion: Fuse concatMap/map
Found:
  concatMap checkBench (map snd $ condBenchmarks pkg)
Perhaps:
  concatMap (checkBench . snd) (condBenchmarks pkg)

so it is immediate for a user to pick it up and append -i "Fuse concatMap/map" to the command (compare with “having to scan hlint --help for the correct option”).

[ffaf1]

I have a rough, working implementation of this. #8427 needs to be merged first.