Convert RpcBlock to an enum that indicates availability #24899

Job	Run time
target-branch-check	3s
Check for 'skip-ci' label	2s
lockbud	40s
check-msrv	5m 7s
check-code	13m 58s
op-pool-tests	6m 22s
network-tests	11m 7s
slasher-tests	1m 18s
http-api-tests	19m 59s
state-transition-vectors-ubuntu	2m 27s
cli-check	6m 34s
release-tests-ubuntu	13m 51s
cargo-udeps	7m 18s
compile-with-beta-compiler	13m 33s
execution-engine-integration-ubuntu	7m 56s
ef-tests-ubuntu	6m 56s
beacon-chain-tests	13m 0s
basic-simulator-ubuntu	13m 10s
debug-tests-ubuntu	4m 17s
cargo-sort	23s
fallback-simulator-ubuntu	10m 50s
test-suite-success	6s
	2h 38m 57s

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