Minor sov-db improvements

[preston-evans98]

Description

This PR makes three minor changes to the sov-db crate:

• Re-export the rocksdb crate so that consumers can access its public types. This is useful for configuration.
• Add the size of the serialized value to the item yielded by DB::Iterator.
• Use get_pinned_cf instead of get_cf inside of the get<T> method to avoid an unnecessary allocation.

Testing

This change is covered by existing tests.

[codecov]

Codecov Report

Merging #1220 (946746d) into nightly (db52671) will decrease coverage by 0.1%.
Report is 4 commits behind head on nightly.
The diff coverage is 75.0%.

Additional details and impacted files

Files	Coverage Δ
full-node/db/sov-db/src/native_db.rs	98.6% <100.0%> (ø)
full-node/db/sov-schema-db/src/iterator.rs	98.8% <100.0%> (+0.1%)	⬆️
full-node/db/sov-schema-db/src/lib.rs	91.5% <100.0%> (ø)
full-node/db/sov-db/src/ledger_db/mod.rs	90.8% <33.3%> (ø)
full-node/db/sov-db/src/state_db.rs	92.9% <40.0%> (-2.6%)	⬇️

... and 23 files with indirect coverage changes