refactor: consider having a separate ticker/thread(from TSS intx observation) for posting block headers

[ws4charlie]

Describe the Issue Here is the current code with the TODO notation.

Expected Outcome Instead of embedding block header posting logic in function observeTssRecvd, we should have a separate/dedicated job or thread for that purpose.

Reason The job of observeTssRecvd scans incoming txs to TSS address in block range [startBlock, toBlock] which will not be always the correct range for block header posting. Adding block header to zetacore is a very sequential process in zetacore and usually slower than inbound tx observation which is posting discrete votes. Decoupling the two makes code more maintainable and less error prone.