* Move DatabaseTest and DatabaseSQLTest to libs,
and remove MediaWikiTestCase dependency.
* Refactor DatabaseTest to be a test of the Database abstract class,
not of whatever current DB backend is configured by LocalSettings.
- Remove most switches/conditionals and other tests for specific
database backends. Move those to individual test classes for
those backends instead.
- Some tests appear to have been integration tests for the PHP driver
and/or the db backend itself. Moved to a new DatabaseIntegrationTest.
- Now that only the abstract Database is invoked, the test runs a bit
faster (no real connections/queries).
* Add missing @covers tags, and remove or fix broken ones
(follows-up 26e52f0c49).
Change-Id: I9dc4a558e701d00e95789e7eb8e02926783b65ad
