Fix stats reporting delays in logical parallel apply worker

Hi,

When implementing another feature, I noticed that parallel apply workers
currently do not report statistics while idle in their main loop. This can cause
stats from the last processed transaction to be arbitrarily delayed, especially
when there are long gaps between streamed transactions.

The issue is demonstrated in 0002, where a TAP test fails when attempting to
collect stats from a parallel apply worker that has no subsequent transaction to
trigger a stats report.

0001 fixes this issue by forcing a stats report when the worker is idle in the
main loop, matching the behavior already present in LogicalRepApplyLoop() for
regular logical apply workers.

Best Regards,
Hou zj