Add a new 3D Viewer window

[RasmiaKulan]

Current Behaviour

Currently, Mantid Imaging does not contain a dedicated window for the 3D Viewer, and therefore there is no placeholder area in the UI for hosting or interacting with 3D content.

Desired Behaviour

Create a window within Mantid Imaging that will serve as the container for interacting with the 3D Viewer. This provides the skeletal structure into which the CILViewer widget can later be embedded.

Potential Pitfalls or Risks to Avoid

Ensure the new window does not conflict with existing window layouts or docking behaviours.

Importance of Feature

A 3D Viewer window is a prerequisite for embedding the CILViewer widget.