CB-7459 Allow automatic tests to be run for specific plugin(s)

Implementation for https://issues.apache.org/jira/browse/CB-7459

See comments in commits for more details.
cdvtests module has a `requireAllTestModules` method which "loads" tests without defining auto/manual tests.  This is an initialization step which is needed to get the list of plugin tests.  I think that instead of passing a "setupEnabler" helper to defineAutoTests, perhaps we should export the `requireAllTestModules` (perhaps rename it to `init` or something`), then we can use the `cdvtests.tests` object directly to iterative test keys/titles/toggle enabled.
WDYT?