Improved speed and specificity in test suite

[Felix Lechner <felix.lechner@lease-up.com>]

Hi,

For tests associated with a check, Lintian now only runs that check.
Almost all tests benefit from this change.

It makes it easier to write tests. Expected tags now relate to only
one check. For most tests, nuisance tags such as
'debian-watch-does-not-check-gpg-signature' are gone.

It also improves the existing body of tests. Most of them are bulky
and non-specific. At one point, many were duplicated. A copy was
placed with each check to which it was somehow related. This
differentiates the expected tags for the copies. It is now easier to
remove test parts that are unrelated to the check tested.

Over time, many tests should become lighter in weight and more focused
on a single tag.

Another great benefit is speed. Preliminary samples show that the test
suite now runs from 20% to 33% faster.

Kind regards
Felix Lechner