Support readonly hasura instance

#7029

### Version Information

Server Version: v2.8.3
CLI Version: 2.4.0

### Environment

Ubuntu 20.04.4 LTS
Docker Community Engine 20.10.13

### The problem

There are cases when we need full read-only connection to inspect entirely functional hasura .
Now it crashes with permission error on start of the hasura instance, cause it tries to modify metadata db.
Real case example - a service of the system works only via hasura, you wanna debug some specific case locally; you need local hasura instance for the local service instance, but connect it to db via specific read-only user. You must avoid any databases modifications, you just wanna read and process read queries.
It would be great if there would be an option for full read only operating.