Fitting Window: Create a Drop Down ROI Menu Widget

[ashleymeigh2]

Issue Closes #2385

Description

Implemented a ROI Selection Widget (ROISelectionWidget) to allow users to select one ROI from the ROIs created within the Fitting Window. This widget is part of the ongoing redesign of the Spectrum Viewer.

Developer Testing

• I have verified unit tests pass locally: python -m pytest -vs
• Tested the dropdown menu behavior when ROIs are added and removed.
• Ensured the dropdown updates dynamically and maintains the selected ROI if it still exists.
• Verified that ROI_RITS is excluded from the dropdown menu.
• Checked that the first available ROI is selected if the previous ROI was deleted.
• Ensured that selectionChanged only emits when the actual selection changes.

Acceptance Criteria and Reviewer Testing

• Unit tests pass locally: python -m pytest -vs
• Verify that the dropdown updates correctly when ROIs are added or removed.
• Test that the selection remains on the same ROI if it still exists after an update.
• If the previous ROI is deleted, ensure the dropdown selects the first available ROI.
• Ensure no unnecessary selectionChanged signals are emitted.

Documentation and Additional Notes

• Release Notes have been updated
• Sphinx documentation has been updated
• Screenshot tests have been updated
  • Before merge for developer: Resolve the change on Applitools by creating a new baseline for the test and verify that the tests pass.
  • After merge for reviewer: Go to Applitools compare and merge page, select all changes, and merge the dev branch into the default branch.
  • After merge for reviewer: Verify that other PR's screenshot tests do not start to fail (See Applitools baselines for more info).

[coveralls]

coverage: 72.662% (-0.2%) from 72.846%
when pulling 6c35dc5 on 2385_ROI_drop_down_widget
into c409e60 on main.