(test) chore: split out backends #20280

Job	Run time
lint	1m 38s
backend-unit-test	3m 29s
backend-de-unit-test	4m 24s
backend-wmg-unit-test	3m 0s
processing-unit-test	5m 17s
backend-integration-test	3m 52s
cellguide-pipeline-unit-test	6m 21s
cxg-admin-unit-test	2m 25s
wmg-processing-unit-test	4m 42s
publish-test-report	1m 44s
submit-codecoverage	2m 18s
	39m 10s

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