Switched the _cluster API body to the AWS supported flat format #8535

Job	Run time
Api Tests (Py 3.8)	10m 22s
Core Tests (Py 3.8)	10m 59s
Docker build	1m 59s
Api Tests (Py 3.9)	9m 46s
Core Tests (Py 3.9)	11m 25s
Api Tests (Py 3.10)	11m 44s
Core Tests (Py 3.10)	10m 0s
Migration Tests	2m 33s
Api Tests (Py 3.11)	12m 14s
Core Tests (Py 3.11)	10m 21s
Docker test circ-scripts (linux/amd64)	1m 26s
Docker test circ-webapp (linux/amd64)	1m 50s
Docker test circ-scripts (linux/arm64)	3m 41s
Docker test circ-webapp (linux/arm64)	3m 17s
Push circ-scripts	1m 35s
Push circ-webapp	1m 31s
Push circ-exec	1m 37s
	1h 46m 20s

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