Refactoring for SpectrumROI

[samtygier-stfc]

Work on #2378

Description

Refactoring for SpectrumROI
Remove some unnecessary methods simplify others

Needs rebase after #2500

Developer Testing

I have tested manually and run system tests

Acceptance Criteria and Reviewer Testing

• Unit tests pass locally: python -m pytest -vs
• In spectrum viewer
  • Adding and removing ROIs
  • Renaming ROIs
  • Changing ROI colour
  • Resizing ROI from image view or properties

Documentation and Additional Notes

Not needed

[coveralls]

coverage: 72.846% (-0.02%) from 72.87%
when pulling 4ee4026 on 2378-refactor-roi
into 65f8cf5 on main.

[MikeSullivan7]

Should self.roi_dict: dict[str, ROI] = {} in SpectrumWidget not be self.roi_dict: dict[str, SpectrumROI] = {} as we use SpectrumROI methods on it, e.g. adjust_spec_roi().

Also we have roi_dict: dict[str, ROI] on line 112 and self.roi_dict: dict[str, ROI] = {} on line 141 which is unnecessary.

[samtygier-stfc]

Good spot. That gives some stricter type checking else where, so needed to fix the type for colour in a few places.

[MikeSullivan7]

All changes look good, code is a lot more streamlined and easier to read now. All tests pass and Spectrum Viewer behaves as expected when going through usual workflows of using the ROIs.