RE: speed up a logical replica setup

Dear Fabrízio, Euler,

I made fix patches to solve reported issues by Fabrízio.

* v13-0001: Same as v11-0001 made by Euler.
* v13-0002: Fixes ERRORs while dropping replication slots [1].
           If you want to see codes which we get agreement, please apply until 0002.
=== experimental patches ===
* v13-0003: Avoids to use replication connections. The issue [2] was solved on my env.
* v13-0004: Removes -P option and use primary_conninfo instead.
* v13-0005: Refactors data structures

[1]: https://www.postgresql.org/message-id/CAFcNs%2BrSG9DcEewsoA%3D85DXhSRh%2BnyKrrcr64FEDytcZf6QaEQ%40mail.gmail.com
[2]: https://www.postgresql.org/message-id/CAFcNs%2BpPtw%2By7Be00BK0MBpHhLk2s66tLM286g%3Dk5rew8kUxjg%40mail.gmail.com

Best Regards,
Hayato Kuroda
FUJITSU LIMITED
https://www.fujitsu.com/