Test hidden API dark grey & pre-P vs P

Hidden API blacklist test would only test the blacklist against
the current API level. Now that we have populated the dark greylist,
we should test the dark greylist too.

We add:
(a) dark greylist enforcement test to the existing test against
    current API level
(b) a new instance of the test which only enforces the blacklist
    against level 27 (Android 8.1)

Bug: 64382372
Test: atest CtsHiddenApiBlacklistCurrentApiTestCases
      atest CtsHiddenApiBlacklistApi27TestCases

Change-Id: Ia238e77cd199993dd24e3ea6421ef95a55df4079
8 files changed