[ proxysql ] add storageclass to data dir and mysql_replication_hostgroups to values.yaml

[allanian]

Hello,
your proxysql is working very nice, thx for you work!,
can we add this things:

1. mysql_replication_hostgroups to values.yaml, current solution with id dont worked on my side,
   i tried do this with this helm block to values.yaml, but its not come to proxysql, when i do a query -
   select * from mysql_replication_hostgroups;

        mysql_replication_hostgroups:
          - comment: "cluster1"
            writer_hostgroup: "1"
            reader_hostgroup: "2"

if i do this manually, its working, before next reboot of proxysql
INSERT INTO mysql_replication_hostgroups (writer_hostgroup,reader_hostgroup,comment) VALUES (1,2,'cluster1');
2) storageclass for saving configs, each reboot/restart daemonset proxysql, clean my mysql_replication_hostgroups