Updating analysator to a python package structure and renaming to analysator

[alhom]

This PR changes quite a bit, but the changes are to the module/package layout and the inclusion of a build system.

It is built to be a drop-in replacement (with deprecation warnings to update scripts):
import pytools will work but will also complain to rename the import to import analysator.

This PR enables installing analysator via pip (see README), suggested pip install -e [path-to-analysator-repo] for installing. Pip will thereafter handle installation of dependencies at their relevant versions automatically.

Pip install will also handle installing the VTK library, for which there is also an experimental interface contained within the PR. With the VTK interface, there is also a rudimentary ParaView plugin as well!

[alhom]

Extra features (isosurface, vtk, and specifically bvtk with more stringent version requirements) got their own entries in the import test matrix. pip install is now used to install dependencies in the tests, so this looks good to on that side as well.

To get all the necessary dependencies:
pip install --editable <path-to-analysator>[all] will now get your the latest and greatest features, them being separately obtainable via [isosurface] (supposing Python >3.8) and [vtk] (fetching VTK > 9.2 for hypertreegrid support).
Maybe this should be default behaviour - is anything still stuck with Python <=3.8?

pip install --editable <path-to-analysator>[bvtk] will get you the version of VTK (9.2.6) which is supported by BVTKnodes. This supposes Python < 3.12.