Rework Validator Client fallback mechanism #18604

Job	Run time
target-branch-check	1s
check-msrv	5m 1s
Check for 'skip-ci' label	1s
check-code	9m 32s
beacon-chain-tests	20m 27s
release-tests-ubuntu	33m 27s
op-pool-tests	15m 55s
release-tests-windows	40m 28s
basic-simulator-ubuntu	13m 21s
cargo-udeps	7m 19s
cli-check	8m 12s
compile-with-beta-compiler	13m 55s
debug-tests-ubuntu	5m 26s
ef-tests-ubuntu	8m 4s
execution-engine-integration-ubuntu	13m 47s
fallback-simulator-ubuntu	11m 4s
network-tests	18m 16s
slasher-tests	1m 38s
state-transition-vectors-ubuntu	2m 25s
test-suite-success	4s
	3h 48m 23s

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