Refactor CI workflow and enable parallelization #126

Job	Run time
build	1m 12s
test_make_docker_configuration	14s
docs	1m 47s
test_main (1)	5m 5s
test_main (2)	5m 28s
check	2m 49s
locales	3m 6s
test_main (3)	5m 33s
test_static_assets	2m 52s
test_es_tests	4m 28s
test_main (4)	4m 52s
test_main (5)	5m 46s
test_internal_routes_allowed	3m 21s
test_main (6)	6m 0s
test_main (7)	5m 35s
test_needs_locales_compilation	3m 14s
test_main (8)	6m 13s
test_main (9)	5m 31s
test_main (10)	5m 4s
upload_durations	7s
	1h 18m 17s

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