Improve performance of get_all_groups_of_choices #537

Job	Run time
call / setup_jobs	7s
call / static (8.3, MOODLE_500_STABLE, pgsql)	1m 27s
call / sync_pull_request_template	0s
call / test (8.1, MOODLE_401_STABLE, pgsql)	11m 25s
call / test (8.1, MOODLE_404_STABLE, pgsql)	17m 53s
call / test (8.1, MOODLE_405_STABLE, pgsql)	17m 43s
call / test (8.0, MOODLE_401_STABLE, pgsql)	11m 22s
call / test (8.3, MOODLE_404_STABLE, pgsql)	14m 6s
call / test (8.1, MOODLE_405_STABLE, mariadb)	10m 19s
call / test (8.1, MOODLE_405_STABLE, mysqli)	10m 55s
call / test (8.3, MOODLE_405_STABLE, mysqli)	11m 34s
call / test (8.2, MOODLE_500_STABLE, pgsql)	11m 48s
call / test (8.2, MOODLE_405_STABLE, pgsql)	15m 34s
call / test (8.3, MOODLE_405_STABLE, mariadb)	10m 57s
call / test (8.2, MOODLE_405_STABLE, mysqli)	11m 44s
call / test (8.2, MOODLE_404_STABLE, pgsql)	16m 3s
call / test (8.3, MOODLE_405_STABLE, pgsql)	17m 44s
call / test (8.2, MOODLE_500_STABLE, mariadb)	11m 51s
call / test (8.2, MOODLE_500_STABLE, mysqli)	12m 3s
call / test (8.4, MOODLE_500_STABLE, mysqli)	12m 28s
call / test (8.3, MOODLE_500_STABLE, pgsql)	16m 31s
call / test (8.3, MOODLE_500_STABLE, mariadb)	12m 13s
call / test (8.4, MOODLE_500_STABLE, pgsql)	18m 0s
call / test (8.4, MOODLE_500_STABLE, mariadb)	12m 43s
call / test (8.3, MOODLE_500_STABLE, mysqli)	12m 12s
call / test (8.2, MOODLE_405_STABLE, mariadb)	10m 47s
	5h 9m 29s

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