SANS: Sample Changer

As a SANS scientist I would like a consistent sample changer OPI to be used across all SANS instruments, so that it is easy for me to use any of the SANS instruments without having to learn how individual sample changers operate.

#### Acceptance Criteria
1. The Sample Changer OPI must have two Tabs: main and advanced.
1. On the main tab:
1. The Sample Changer OPI must allow me to select a named presets (i.e. defined sample changer positions)
* the OPI must display setpoint and readback values of the name of the selected preset and the corresponding X and Y coordinates
* the OPI must indicate if the sample changer is moving to the selected preset
1. On the advanced tab:
1. The Sample Changer OPI must allow me to define dynamic offsets for the
* the OPI must display setpoint and readback values the dynamic offsets
1. The Sample Changer OPI must allow me to view motor details for the motors that move the sample changer on the X and Y axes
1. The Sample Changer OPI must allow me to view and edit presets (i.e. the underlying motion setpoints)
1. The Sample Changer OPI must allow me to reload the presets (e.g. after they have been edited).

#### Notes
1. SANS instruments are: SANS2D, LOQ, ZOOM, LARMOR.
1. LOQ, ZOOM, LARMOR all have existing sample changer OPIs and use the motion set points mechanism. This ticket is less about implementing new functionality and is more concerned with how the existing functionality is presented.
1. Each of these features will be implemented via a seperate ticket (so that functionality can be built up and delivered incrementally). See **Implementation Tickets** below.
1. The new sample changer OPI should be deployed one instrument at a time. It will need careful configuration for each instrument because, in order to have a consistent sample changer OPI, axis conventions on some instruments will need to change. The suggested order of deployment is: 1-SANS2D, 2-LOQ, 3-ZOOM, 4-LARMOR.

#### Implementation Tickets
- [x] #5720 SANS: Sample Changer - select preset positions
- [x] #5721 SANS: Sample Changer - dynamic offsets
- [x] #5722 SANS: Sample Changer - View Motors
- [ ] #5723 SANS: Sample Changer - View Presets
- [ ] ~~#5724 SANS: Sample Changer - Edit Presets~~
- [x] #5725 SANS: Sample Changer - Reload Presets