Add support for MSSQL #652

Job	Run time
CI test (make validate)	1m 1s
Code coverage (codecov)	1m 1s
Build moodle-plugin-ci.phar	27s
Integration tests (8.3, main)	6m 17s
Integration tests (8.3, MOODLE_404_STABLE)	6m 50s
Integration tests (8.2, MOODLE_403_STABLE)	5m 56s
Integration tests (8.2, MOODLE_402_STABLE)	6m 36s
Integration tests (8.1, MOODLE_401_STABLE)	7m 0s
Integration tests (8.0, MOODLE_400_STABLE)	6m 27s
Integration tests (8.0, MOODLE_311_STABLE)	6m 0s
Integration tests (7.4, MOODLE_39_STABLE)	6m 6s
Integration tests (PHAR) (8.3, main)	5m 57s
SelfUpdate tests (PHAR) (8.3)	36s
Integration tests (PHAR) (8.3, MOODLE_404_STABLE)	6m 3s
SelfUpdate tests (PHAR) (8.2)	30s
Integration tests (PHAR) (8.2, MOODLE_403_STABLE)	5m 51s
SelfUpdate tests (PHAR) (8.1)	24s
Integration tests (PHAR) (8.1, MOODLE_402_STABLE)	5m 31s
SelfUpdate tests (PHAR) (8.0)	44s
Integration tests (PHAR) (8.0, MOODLE_401_STABLE)	7m 26s
SelfUpdate tests (PHAR) (7.4)	13s
Integration tests (PHAR) (7.4, MOODLE_400_STABLE)	5m 56s
	1h 32m 52s

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