Separate requirements

[paskino]

The full functionality of the viewer depends on a few packages:

CILViewer/Wrappers/Python/conda-recipe/meta.yaml

Lines 33 to 43 in 1bcf7a3

	run:
	- python >=3.7
	- numpy
	- vtk
	- pyside2
	- eqt>=1.0.0
	- importlib_metadata # [py<38]
	- h5py
	- pyyaml
	- schema
	- cil-data =22.0.0

1. VTK, absolutely necessary
2. Qt and pyside2 via eqt, to embed the viewer in GUIs and for async process
3. other packages like schema or h5py which are necessary for reading

I think that the raw viewer should work with just VTK. Only if you want to build a Qt application you should install Qt and the rest.
However, currently random imports of eqt dialogs, or libraries for reading files are scattered here and there, so in the end you need to install all of that.