Summary:
All commands now have `--verbosity` flag, so one can configure
cabal package with `--hpc-options="--verbosity=0"`.

Right now it is used only in `hpc markup` to supress unnecessary
output.

Reviewers: austin

Reviewed By: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D660

GHC Trac Issues: #10091