Convert RpcBlock to an enum that indicates availability #18001

Job	Run time
dockerfile-ubuntu	8m 59s
doppelganger-protection-failure-test	6m 55s
checkpoint-sync-test-sepolia	9m 52s
doppelganger-protection-success-test	10m 23s
run-local-testnet	9m 50s
genesis-sync-test-electra-120s	4m 40s
genesis-sync-test-fulu-120s	5m 18s
genesis-sync-test-electra-300s	9m 46s
genesis-sync-test-fulu-300s	9m 52s
local-testnet-success	1s
	1h 15m 36s

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