Embed pymysql within the collection and use default test container

This change eliminates the need to install the connector on each
controlled node, as `pymysql` version 1.1.1 is now included. As a
result, we can safely assume its availability, thus simplifying the
testing process.

Also, I managed to remove the need for pre-built test containers. We
now use the default test containers from ansible-test.

plugins/modules/mysql_query.py

@@ -26,9 +26,7 @@ options:
       as a formatting character. All literal C(%) characters in the query should be
       escaped as C(%%).
     - Note that if you use the C(IF EXISTS/IF NOT EXISTS) clauses in your query
-      and C(mysqlclient) or C(PyMySQL 0.10.0+) connectors, the module will report
-      that the state has been changed even if it has not. If it is important in your
-      workflow, use the C(PyMySQL 0.9.3) connector instead.
+      the module will report that the state has been changed even if it has not.
     type: raw
     required: true
   positional_args:
@@ -126,7 +124,6 @@ from ansible_collections.community.mysql.plugins.module_utils.mysql import (
     mysql_connect,
     mysql_common_argument_spec,
     mysql_driver,
-    mysql_driver_fail_msg,
 )
 from ansible.module_utils._text import to_native
 
@@ -189,9 +186,6 @@ def main():
     else:
         arguments = None
 
-    if mysql_driver is None:
-        module.fail_json(msg=mysql_driver_fail_msg)
-
     # Connect to DB:
     try:
         cursor, db_connection = mysql_connect(module, login_user, login_password,