Remove the streaming files for incomplete xacts after restart.

Remove the streaming files for incomplete xacts after restart.

After restart, we try to stream the changes for large transactions that
were not sent before server crash and restart. However, we forget to send
the abort message for such transactions. This leads to spurious streaming
files on the subscriber which won't be cleaned till the apply worker or
the subscriber server restarts.

Reported-by: Dilip Kumar
Author: Hou Zhijie
Reviewed-by: Dilip Kumar and Amit Kapila
Backpatch-through: 14
Discussion: https://postgr.es/m/OS0PR01MB5716A773F46768A1B75BE24394FB9@OS0PR01MB5716.jpnprd01.prod.outlook.com