chore(tech): split out backends #20277

Job	Run time
backend-unit-test	5m 4s
backend-wmg-unit-test	4m 41s
lint	1m 44s
processing-unit-test	5m 11s
backend-de-unit-test	3m 4s
backend-integration-test	3m 22s
cellguide-pipeline-unit-test	6m 27s
cxg-admin-unit-test	2m 17s
wmg-processing-unit-test	4m 48s
submit-codecoverage	2m 41s
publish-test-report	1m 23s
	40m 42s

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