Convert RpcBlock to an enum that indicates availability #17928

Job	Run time
dockerfile-ubuntu	8m 38s
checkpoint-sync-test-sepolia	4m 25s
doppelganger-protection-failure-test	6m 48s
run-local-testnet	27m 13s
doppelganger-protection-success-test	11m 49s
genesis-sync-test-electra-300s	7m 10s
genesis-sync-test-electra-120s	4m 29s
genesis-sync-test-fulu-300s	7m 38s
genesis-sync-test-fulu-120s	4m 21s
local-testnet-success	10s
	1h 22m 41s

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