Refactor (ci): Use a `job_group_key` to group jobs #166

Job	Run time
build-2-4-4	52s
build-2-4-11	45s
build-2-3-18	19s
build-2-4-12	21s
build-2-4-6	36s
build-2-5-8	23s
build-2-6-5	49s
test-nogitdiff	1m 54s
publish-draft-release	0s
update-dockerhub-description	0s
update-draft-release	0s
	5m 59s

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