[Storage] Open db in parallel when storage sharding is enabled. #71570

Job	Run time
file_change_determinator	10s
rust-doc-tests	5m 20s
rust-consensus-only-unit-test	0s
rust-consensus-only-smoke-test	0s
rust-unit-tests	0s
rust-cargo-deny	1m 40s
rust-lints	3m 40s
rust-smoke-tests	27m 12s
general-lints	27s
rust-check-merge-base	1m 20s
rust-build-cached-packages	2m 4s
rust-cryptohasher-domain-separation-check	0s
rust-targeted-unit-tests	9m 43s
	51m 36s

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