ENH: Add cxx test cases for testing smtk export

Add Cxx testing for vtkSlicerSMTKFileWriterLogic. Tests include exporting into smtk format:

1. Empty scene
2. poly data mrml node
3. Image data mrml node
4. segmentation mrml node

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Additionally, build tree launcher settings were updated with correct paths for MOAB, aeva-session, and smtk.

Update: These changes have been integrated independently in !6 (merged) and the topic has been rebased against master and forced push.

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Finally, memory leaks were detected in aeva-session after adding tests (particularly: vtkSlicerSMTKFileWriterLogicExportPolyDataTest) that are fixed through the following MR: session!112 (merged)

This addresses issue aevaSlicer issue: #3 (closed)