* By default use V=0, and call the testsuite with VERBOSE=2, which we
    did before only with validate --quiet. This disables printing the
    test commands it runs.

  * When --quiet is used, call the testsuite with VERBOSE=1. This
    disables printing the '====> Scanning' lines, and doesn't print
    which test is being run. So it only prints something when a test
    accidentally prints to stdout or when it fails.

    Don't set this option on Travis, as Travis will cancel a build if it
    doesn't see any output for more than 10 minutes.

  * When --quiet is used, set the new test option NO_PRINT_SUMMARY,
    which skips printing the test summary. Only the list of unexpected
    failures is printed, if there are any. Note that the full summary
    can still be found in testsuite_summary.txt

  * When --quiet is used, don't pass the `-v` flag to `ghc-pkg check`

  * When --quiet is used, don't print the Oops! header. It shoud be
    clear from the list of failing tests that something is wrong.

This is all done to get the most out of 30 lines of logfile. These changes can
be disabled later by simply not passing the --quiet flag to validate.

Differential Revision: https://phabricator.haskell.org/D942