Add test for pg_recvlogical reconnection behavior.

Add test for pg_recvlogical reconnection behavior.

This commit adds a test to verify that data already received and flushed by
pg_recvlogical is not streamed again even after the connection is lost,
reestablished, and logical replication is restarted.

Author: Mircea Cadariu <cadariu.mircea@gmail.com>
Co-authored-by: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CAHGQGwFeTymZQ7RLvMU6WuDGar8bUQCazg=VOfA-9GeBkg-FzA@mail.gmail.com