Tests

feat: restructure Part2 database crate #4300

Job	Run time
check	29s
check no_std	28s
clippy	1m 14s
check serde	38s
check no_std kzg-rs	37s
check std	24s
docs	1m 1s
fmt	9s
test stable --no-default-features	44s
test stable	58s
TyposCheck	5s
test stable --all-features	1m 29s
test beta --no-default-features	1m 4s
test beta	1m 2s
test beta --all-features	1m 24s
test nightly --no-default-features	50s
test nightly	48s
test nightly --all-features	1m 8s
	14m 32s

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