POLREF: Add current/voltage dials for GMW magnet

As an instrument scientist (CK) on POLREF I would like dials on my OPI for voltage for current (see https://github.com/ISISComputingGroup/IBEX/issues/7399).

In order for this to be implemented, some discussion needs to be had about how to fit this large widgets onto an already crowded DFKPS OPI: as the Field group is itself an embedded OPI, in order to insert these dials in that group you would need to duplicate the main dfkps OPI, as well as the calibrated/uncalibrated OPIs. If you don't embed the dials into the Field group, it reduces the usability of the OPI (see `\\isis\shares\ISIS_Experiment_Controls\data for tickets\Ticket7474` for example image).

### Acceptance Criteria
_What is the acceptance criteria?_
- [ ] Dials for current and voltage are implemented for the GMW Magnet

### Extra Information
_Why it is needed?_

_Where required files/links are_

## How to Test
_verbose instructions for reviewer to test changes
(**Add before making a PR**)_