Fix state-db pinning

[arkpar]

A follow up to #12902. Previous PR did not account for the possibility of multiple blocks finalized in a single transaction. This version accumulates all canonicalized changes pinned in memory, until explicitly released with the sync function. Similar to apply_changes function that existed before the state-db refactoring.

[cheme]

Maybe rename sync method with commit_cannonicals or something more related to commit_operation (commit_synch maybe).

[arkpar]

I went for a more general name. It basically means that the in-memory state is synchronized with the on-disk state.

[bkchr]

Suggested change

	let mut pinned = std::mem::take(&mut self.pinned_canonincalized);
	for hash in pinned.iter() {
	self.unpin(hash)
	}
	pinned.clear();
	self.pinned_canonincalized.drain(..).for_each(|h| self.unpin(h));

[arkpar]

This won't work because drain iterator borrows &mut self and unpin requires &self

[bkchr]

Good point, but the call to clear is also not really required.

[arkpar]

bot merge