Convert RpcBlock to an enum that indicates availability #18002

Job	Run time
dockerfile-ubuntu	8m 28s
doppelganger-protection-success-test	12m 5s
genesis-sync-test-fulu-120s	5m 22s
run-local-testnet	26m 54s
checkpoint-sync-test-sepolia	5m 22s
genesis-sync-test-fulu-300s	8m 11s
genesis-sync-test-electra-300s	8m 41s
doppelganger-protection-failure-test	7m 14s
genesis-sync-test-electra-120s	5m 4s
local-testnet-success	9s
	1h 27m 30s

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