[Syncer] Save stage_batches progress in intervals

[V-Staykov]

Rationale

Why should this feature exist?

Currently stage batches doesn't save the downloaded batches until the end of the stage. If it is interrupted - the DB transaction is reverted. In some cases this could lose a lot of quality data that will have to be downloaded again.

What are the use-cases?

Some networks like zkEvm Mainnet and XLayer have a lot of blocks and even stage_batches takes some time to run. It won't take much to make it save it's progress each 2m blocks or so.

Implementation

Do you have ideas regarding the implementation of this feature?

Make it commit the tx and create a new once a saved blocks counter reaches 2m or so.