add ordered db feature gate #69

Job	Run time
clippy	1m 3s
check	24s
check no_std	27s
check serde	29s
check no_std optimism	28s
docs	1m 23s
check std	27s
fmt	12s
test stable --no-default-features	56s
test stable	1m 13s
test stable --features="all, scroll"	57s
test stable --features="all, optimism"	1m 30s
test beta --no-default-features	1m 10s
test beta	1m 9s
test beta --features="all, scroll"	54s
test beta --features="all, optimism"	1m 33s
test nightly --no-default-features	45s
test nightly	54s
test nightly --features="all, scroll"	52s
test nightly --features="all, optimism"	1m 18s
	18m 4s

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