Add unix socket tests

[Nothing4You]

What do these changes do?

Run the entire test suite against unix sockets as well as over TCP.
This effectively runs every test twice against every DB version, once over unix socket, once over TCP.

This also implements passing arbitrary connection info to the test suite, allowing to run tests against multiple databases in the same test run.
It can later be expanded to run more databases in the same test run, which should allow us to launch containers for all databases in the same CI job (assuming CI VM resource limits permit that).
For that to be implemented however, the current workaround of passing DB versions via env var needs to be replaced.

Due to doing even more changes to the service containers with this it may be worth to just not use service containers at all in the future, launching custom containers by ourselves at an early step.
That may also benefit testing on other OS, as service containers are currently only supported on ubuntu.

Are there changes in behavior for the user?

No.

Related issue number

Fixes #664

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• Add a new news fragment to CHANGES.txt

[codecov]

Codecov Report

Merging #686 (1dbd5e9) into master (8fe7e53) will decrease coverage by 1.91%.
The diff coverage is 62.50%.

❗ Current head 1dbd5e9 differs from pull request most recent head 549dd46. Consider uploading reports for the commit 549dd46 to get more accurate results

@@            Coverage Diff             @@
##           master     #686      +/-   ##
==========================================
- Coverage   85.68%   83.76%   -1.92%     
==========================================
  Files          12       12              
  Lines        2088     2088              
  Branches      336      336              
==========================================
- Hits         1789     1749      -40     
- Misses        229      271      +42     
+ Partials       70       68       -2     

Flag	Coverage Δ
ubuntu-latest_3.7_mariadb-10.2	82.50% <62.50%> (+0.58%)	⬆️
ubuntu-latest_3.7_mariadb-10.3	82.50% <62.50%> (+0.58%)	⬆️
ubuntu-latest_3.7_mariadb-10.4	82.50% <62.50%> (+0.58%)	⬆️
ubuntu-latest_3.7_mariadb-10.5	82.50% <62.50%> (+0.58%)	⬆️
ubuntu-latest_3.7_mariadb-10.6	82.50% <62.50%> (+0.58%)	⬆️
ubuntu-latest_3.7_mariadb-10.7	82.50% <62.50%> (+0.58%)	⬆️
ubuntu-latest_3.7_mysql-5.7	83.38% <62.50%> (+0.58%)	⬆️
ubuntu-latest_3.7_mysql-8.0	?
ubuntu-latest_3.8_mariadb-10.2	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.8_mariadb-10.3	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.8_mariadb-10.4	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.8_mariadb-10.5	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.8_mariadb-10.6	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.8_mariadb-10.7	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.8_mysql-5.7	83.76% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.8_mysql-8.0	?
ubuntu-latest_3.9_mariadb-10.2	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.9_mariadb-10.3	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.9_mariadb-10.4	82.90% <62.50%> (?)
ubuntu-latest_3.9_mariadb-10.5	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.9_mariadb-10.6	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.9_mariadb-10.7	82.90% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.9_mysql-5.7	83.76% <62.50%> (+0.57%)	⬆️
ubuntu-latest_3.9_mysql-8.0	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
aiomysql/connection.py	78.31% <62.50%> (-4.39%)	⬇️
aiomysql/pool.py	95.18% <0.00%> (-1.81%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8fe7e53...549dd46. Read the comment docs.

[Nothing4You]

somehow codecov broke...
continuing in a new pr

[Nothing4You]

replaced by #696