Modularize beacon node backend #19589

Job	Run time
check-code	13m 41s
Check for 'skip-ci' label	1s
check-msrv	5m 23s
lockbud	14m 18s
target-branch-check	1s
op-pool-tests	21m 29s
release-tests-ubuntu	27m 57s
beacon-chain-tests	28m 46s
basic-simulator-ubuntu	21m 10s
cargo-udeps	7m 21s
cargo-sort	7s
cli-check	14m 11s
compile-with-beta-compiler	15m 7s
debug-tests-ubuntu	7m 59s
ef-tests-ubuntu	8m 2s
execution-engine-integration-ubuntu	13m 11s
fallback-simulator-ubuntu	19m 16s
network-tests	24m 36s
release-tests-windows	32m 43s
slasher-tests	3m 40s
state-transition-vectors-ubuntu	8m 2s
test-suite-success	4s
	4h 47m 5s

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