Convert RpcBlock to an enum that indicates availability #18000

Job	Run time
dockerfile-ubuntu	8m 23s
doppelganger-protection-success-test	9m 13s
checkpoint-sync-test-sepolia	3m 17s
run-local-testnet	8m 58s
doppelganger-protection-failure-test	6m 51s
genesis-sync-test-electra-300s	8m 45s
genesis-sync-test-fulu-300s	8m 23s
genesis-sync-test-fulu-120s	5m 21s
genesis-sync-test-electra-120s	5m 4s
local-testnet-success	1s
	1h 4m 16s

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