Support GRANT ... ON DATABASE TO ...

We don't propagate `GRANT ... ON DATABASE ...` currently

1. log in as superuser
2. CREATE USER myuser
3. GRANT CREATE ON DATABASE postgres TO myuser;
4. connect as myuser
5. CREATE SCHEMA myschema;
6. Now you get an error:
```
ERROR: 42501: permission denied for database postgres
CONTEXT: while executing command on localhost:9701
```

Note: `GRANT CREATE | CONNECT | TEMPORARY | TEMP ...` should all be supported.

Subtask of #4812