Improve auto-completion support

[jcfr]

• Improve VS code auto-completion support #6686
• Generate pyi files for vtk and vtk based classes #6892
  • Generate .pyi files for VTK classes #6688
  • Generate .pyi files for VTK based classes #6689
• Support slicer type annotations in static analysis (Sphinx Autodoc and MyPy). #6875
• Add support for auto-completion of Qt-based classes