[Feature] Support Mutate MySQL user's password

[Nrehearsal]

Is your feature request related to a problem? Please describe.

• It's a bad way to update the user password by deleting and then recreating it, DELETE is dangerous.
• It's may not a k8s style operation.

Describe the solution you'd like

ideas of user's reconciliation

• create user if not exists
• watch userpassword-secret and reconcile user's password with it
• reoncile user's permissions with permissions in mysqluser CR
• users managed by MySQL Operator can no longer change the password in the other way!!!

POC:

mysql> CREATE USER IF NOT EXISTS 'larryhuang'@'%' identified by 'mypassword';
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> SELECT count(1) password_matched from mysql.user where user='larryhuang' and authentication_string=PASSWORD('mypassword');
+------------------+
| password_matched |
+------------------+
|                1 |
+------------------+
1 row in set, 1 warning (0.00 sec)
mysql> UPDATE mysql.user SET authentication_string=PASSWORD('mynewpassword') WHERE user = 'larryhuang';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1
mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.00 sec)

Describe alternatives you've considered

Additional context