Optimize duty performance #117

Job	Run time
cargo-fmt	13s
target-branch-check	0s
compile-with-beta-compiler	22m 46s
extract-msrv	6s
op-pool-tests	25m 21s
beacon-chain-tests	49m 26s
dockerfile-ubuntu	26m 51s
ef-tests-ubuntu	49m 29s
debug-tests-ubuntu	37m 23s
release-tests-ubuntu	49m 30s
release-tests-windows	49m 17s
slasher-tests	6m 43s
state-transition-vectors-ubuntu	17m 55s
arbitrary-check	2m 10s
cargo-audit	4m 44s
cargo-udeps	15m 37s
cargo-vendor	38s
check-benchmarks	8m 36s
check-msrv	10m 15s
clippy	10m 8s
doppelganger-protection-test	47m 8s
eth1-simulator-ubuntu	46m 44s
execution-engine-integration-ubuntu	26m 41s
merge-transition-ubuntu	45m 4s
no-eth1-simulator-ubuntu	47m 11s
syncing-simulator-ubuntu	33m 40s
	10h 33m 36s

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