Convert RpcBlock to an enum that indicates availability #24988

Job	Run time
Check for 'skip-ci' label	2s
check-code	12m 45s
lockbud	45s
target-branch-check	3s
check-msrv	5m 8s
release-tests-ubuntu	14m 1s
op-pool-tests	6m 24s
beacon-chain-tests	13m 1s
slasher-tests	1m 15s
http-api-tests	19m 57s
debug-tests-ubuntu	4m 16s
network-tests	11m 19s
cli-check	6m 27s
ef-tests-ubuntu	7m 0s
cargo-udeps	7m 9s
state-transition-vectors-ubuntu	2m 37s
cargo-sort	32s
fallback-simulator-ubuntu	11m 34s
execution-engine-integration-ubuntu	7m 51s
basic-simulator-ubuntu	13m 22s
compile-with-beta-compiler	14m 5s
test-suite-success	6s
	2h 39m 39s

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