**Description**

We've never run any CI jobs for MySQL 8 in our CI system. All the jobs are running at 5.7. With the recent refractor, it is as easy as changing CURRENT_MYSQL_VERSIONS to include the MySQL 8 and change the Dockerfile.ci to use mysql8 client as well (currently Dockerfile.ci uses MySQL 5.7 client).

I think this is a hard pre-requisite for the HA Scheduler PR (#9630) to be merged. HA scheduler will only work in a single-scheduler mode for MySQL 5.7 and without running the whole test suite for MySQL 8 we might be giving the users who would likely try MySQL 8 version of Airflow that does not really work well. 

This has some consequences: our build will run quite a bit longer (we might limit versions of python to test with it but still this is at least 20% longer. So it would be best if we implement #10507 and pre-requisite for it is #11163.
Otherwise, our PRs will be blocking each other and we will slow down our own development.

Note that implementing it might be as easy as adding the version and changing client and it **just work** but since we did not ever run it, it is likely there will be some problems to solve.

**Use case / motivation**

When HA scheduler will get in hands of our users as first Alpha release, we have to be quite sure that it works also for MySQL 8 because  only with MySQL 8 users will be able to test the HA setup for their MySQL installations.

**Related Issues**

#10507 #11163 


tests/providers/mysql/hooks/test_mysql.py
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import json
import os
import unittest
from unittest import mock
import MySQLdb.cursors
import pytest
from parameterized import parameterized
from airflow.models import Connection
from airflow.models.dag import DAG
from airflow.providers.mysql.hooks.mysql import MySqlHook
from airflow.utils import timezone
SSL_DICT = {'cert': '/tmp/client-cert.pem', 'ca': '/tmp/server-ca.pem', 'key': '/tmp/client-key.pem'}
class TestMySqlHookConn(unittest.TestCase):