Add a button group to allow for proper logic of radio buttons

[rozyczko]

Description

When opencl is not present, the only option on the GPU Options dialog is "No OpenCL".
However, this "radio" button could be deselected and deselecting it caused issues when running tests.

This has been fixed by adding a QButtonGroup to add all the radio buttons into a layout.

Fixes #2841

How Has This Been Tested?

Local Win10 build

Review Checklist:

[if using the editor, use [x] in place of [ ] to check a box]

Documentation (check at least one)

• [X ] There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)

Licencing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)

[juliuskarliczek]

Tested RadioButton functionality on local win10 build with and without pyopencl installed. Works perfectly fine for me. RadioButton cannot be deselected anymore

[krzywon]

With our process for merging release branches back into main, I think this PR should closed in favor of #2848.

[rozyczko]

closing as per comment