[PATCH] Add regression tests of ecpg command notice (error / warning)

Hi hackers,

When I wrote patch of ecpg command notice bug, I recognized needs of
regression tests for ecpg command notices and I say that I write the
tests.

https://commitfest.postgresql.org/52/5497/
https://www.postgresql.org/message-id/0efab1f6-5d8d-451f-a7dc-ef9c73ba9e02%40oss.nttdata.com

This mail is about patch of the tests.

Patch is attached to this mail : ecpg_cmd_notice_regress_test.patch
This patch passed CI.
https://cirrus-ci.com/build/4861827500212224

And corresponding diff is below.
https://github.com/ryogrid/postgres/compare/0ec3c295e7594ed3af86bca1a4b4be269c2f069d...72329311a75630594bcaa38248255360b7e8e525

I explain about implementation of this patch.

What is this patch
- add regression tests which test ecpg command notices such as warning
and errors
- test notices implemented in ecpg.addons file

Basic policy on implementation
- do in a way that matches the method using the existing pg_regress
command as much as possible
- avoid methods that increase the scope of influence

Next, I list answers to points that are likely to be pointed out in
advance below :)
- shell scripts and bat files is used due to ...
avoid non zero exit code of ecpg command makes tests failure
avoid increasing C code for executing binary which cares cross platform
- python code is used because I couldn't write meson.build
appropriately describe dependency about materials which is used on
tests without it. please help me...
- as you said, kick this kind of tests by pg_regress accompanied with
needless PG server process execution. but pg_regress doesn't execute
test without it and making pg_regress require modification which has
not small scope of influence

---
Great regards,
Ryo Kanbayashi
https://github.com/ryogrid