`cabal list` has bad defaults

The 5-line output is silly, you have to grep it regardless so assuming it's going to be read by a human is erroneous due to the volume of text.

Deprecate the option (stderr warning?) that makes it greppable, make that the default.

Start by locating the cabal list command implementation and the option that currently produces greppable output. Check how command-line deprecations are reported; done means the greppable format is the default and the old option emits the intended warning while existing list behavior remains covered.

Written by the indexing model from the issue text.