Reset LastSuccessfulVersion to 0 if Restarting on Stauts=Complete

[dermanyang]

Purpose

If the backfillStatus is Complete on a particular row, while the processor will correctly start to backfill from 0 again, the table will not reflect the current status due to the monotonic increasing invariant set on the table writes. A workaround was to simply remove that invariant.

This PR adds back that invariant to avoid possible edge cases and instead resets the latestSuccessVersion to 0 in the starting_version logic upon encountering the Complete state.

Testing

Manually tested expected behavior:

[yuunlimm]

qq: what specific edge cases led to the removal of the invariant initially?

[dermanyang]

@yuunlimm I initially removed the WHERE clause assuming that given correct processing order and starting_version logic (namely, choosing the MAX of start_ver/latest_processing or restarting given a Completed state) would be sufficient.

But I remembered that we don't actually enforce in-order events so it would be possible to have weird in_progress states that don't actually reflect the processor's progress lol. So I added it back for sanity.