Grant more rights to users with AL privileges (seeing other users jobs / ability to set session to other user)

**Use case**:
As a CrateDB user with **admin privileges** on cluster level I want to be able to run certain commands like setting a session to another user with `SET SESSION AUTHORIZATION username`, as I already have the ability to basically drop, recreate and login as this user anyway. Also changing the password of an existing user should be possible, for pretty much the same reason. This might be needed to stop a long running job (e.g. import of large datasets)

**Feature description**:

Allow the following Statements for users with `AL` privileges:
- `SET [ SESSION | LOCAL ] SESSION AUTHORIZATION username`
This should also make it possible to run `KILL ALL` for jobs started by `username` through the logged in user.

Further users with `AL` privileges should be able to see all running jobs within `sys.jobs` (**maybe** except of superuser `crate`), to identify long running jobs and have a general picture - as admin user - what is happening in the cluster.