Previously, the block gap storage could be updated even when the gap is
the same as before. This patch fixes it by only updating the storage
when the gap is changed.

Pure tiny refactoring, no logical changes.

The benefit of consistent format strings is 10 lines of deletion.

The other style changes are added by the rust formatter.

Previously, the block gap state in `BlockchainDb` in unconditionally updated
whenever `try_commit_operation` is invoked, even if the state hadn't changed.
This commit refines the logic to update the block gap state only when a change
occurs, reducing unnecessary writes and improving efficiency.