Add support for phpunit --testsuite and --filter options #546

Job	Run time
CI test (make validate)	27s
Code coverage (codecov)	0s
Integration tests (8.2, master)	5m 15s
Build moodle-plugin-ci.phar	1m 4s
Integration tests (8.2, MOODLE_403_STABLE)	6m 18s
Integration tests (8.2, MOODLE_402_STABLE)	6m 16s
Integration tests (8.1, MOODLE_401_STABLE)	6m 8s
Integration tests (8.0, MOODLE_400_STABLE)	5m 48s
Integration tests (8.0, MOODLE_311_STABLE)	6m 32s
Integration tests (7.4, MOODLE_310_STABLE)	5m 52s
Integration tests (7.4, MOODLE_39_STABLE)	6m 9s
Integration tests (7.4, MOODLE_38_STABLE)	6m 22s
Integration tests (PHAR) (8.2, master)	5m 15s
Integration tests (PHAR) (8.1, MOODLE_403_STABLE)	7m 45s
Integration tests (PHAR) (8.0, MOODLE_401_STABLE)	8m 47s
Integration tests (PHAR) (7.4, MOODLE_400_STABLE)	4m 46s
	1h 22m 44s

Provide feedback