Confirm chain state after submitting relay entry

[pdyraga]

During the work on application-specific actions in ECDSA client, we abstracted utility allowing to wait for a certain number of blocks to confirm the deposit state, and if the state is not the one we expect, trigger the action again. A similar mechanism can be used to confirm a relay entry has been submitted to the chain to improve the handling of minor-to-mid chain reorgs.

Please see WaitForBlockConfirmations in keep-common.