Revise Siren documentation #18933

Job	Run time
lockbud	11m 6s
check-msrv	5m 5s
check-code	9m 51s
Check for 'skip-ci' label	1s
target-branch-check	1s
beacon-chain-tests	11m 9s
basic-simulator-ubuntu	11m 5s
cargo-udeps	7m 31s
cli-check	6m 11s
compile-with-beta-compiler	11m 4s
debug-tests-ubuntu	11m 9s
ef-tests-ubuntu	8m 24s
execution-engine-integration-ubuntu	11m 8s
fallback-simulator-ubuntu	11m 6s
network-tests	11m 5s
op-pool-tests	11m 10s
release-tests-ubuntu	11m 8s
release-tests-windows	10m 51s
slasher-tests	1m 39s
state-transition-vectors-ubuntu	2m 34s
test-suite-success	1s
	2h 43m 19s

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