Partially reinstates the 3.x style PhpUnitWrapper which was removed in d1af214ef5efb817c14b85b639525104d94ef2d9.
While we no longer need the full wrapper, the part which creates a fake class is still useful.
The preferred alternative would be to remove any references to SapphireTest from non-dev files,
which mostly applies to SapphireTest::is_running_test(). This should be solved in a larger refactor
of SapphireTest into optional traits and more fine grained functionality.
5a7c6d4f60