[Ogre] Fix idvr with mixed rendering

What does this MR do?

Closes #142 (closed)

Side effect: closes #94 (closed)

Also brings a few new buttons to the OgreViewer toolbar and fixes the clipping box update.

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Rendering meshes inside the IDVR countersink geometry is only available for the DepthPeeling and Default core compositors. It would take a lot more time to have working with the DualDepthPeeling, WeightedBlend and Hybrid OIT techniques.

⚠ ⚠

How to test it?

• Run OgreViewer
• Open PATIENT_DICOM.vti from this folder
• Set the OIT technique to Default or DepthPeeling
• Load an organ mask from the above folder.
• Enable MImp IDVR.
• Load a mesh.
• Make sure it doesn't affect the countersink geometry.

Additional tests to run

• run on macOS (@dweckmann, @eharquel, @mschweitzer 🙏)