MDANSE UnitTest fixes

[ChiCheng45]

Description of work
Code changes to get all MDANSE UnitTest working and removed either redundant or obsolete test e.g. test which use MMTK.
Added github workflow to run tests.
Removed python 3.8 support since MDANSE uses newer python features that are not supported in 3.8.
Test under FunctionalTests directory to be fixed in a later pull request.
Cython code changes were made, recompilation of the Cython code will be required.

Fixes
Various fixes across the MDANSE codebase.

To test
Build and run MDANSE UnitTests with pytest.

======================================================================================================= test session starts ======================================================================================================= 
platform win32 -- Python 3.11.7, pytest-7.4.4, pluggy-1.0.0
rootdir: C:\Users\xcb63893\PycharmProjects\MDANSE\MDANSE
plugins: cov-4.1.0
collected 435 items

test_analysis.py ..........                                                                                                                                                                                                  [  2%]
test_atom_selector.py ..................................                                                                                                                                                                     [ 10%]
test_chemical_entity.py ..................................................................................................................................................................................................   [ 54%]
test_configuration.py ...........................................                                                                                                                                                            [ 64%]
test_configurator.py ...                                                                                                                                                                                                     [ 65%]
test_databases.py ...........................................................................                                                                                                                                [ 82%]
test_geometry.py .                                                                                                                                                                                                           [ 82%]
test_molecular_dynamics.py ...                                                                                                                                                                                               [ 83%]
test_pdb_reader.py .                                                                                                                                                                                                         [ 83%]
test_trajectory.py ....                                                                                                                                                                                                      [ 84%]
test_trajectory_utils.py .........                                                                                                                                                                                           [ 86%]
test_unit_cell.py ........                                                                                                                                                                                                   [ 88%]
test_units.py ..............                                                                                                                                                                                                 [ 91%]
Analysis\test_dynamics.py ......                                                                                                                                                                                             [ 93%]
Analysis\test_meansquare.py ...                                                                                                                                                                                              [ 93%]
Analysis\test_qvectors.py .                                                                                                                                                                                                  [ 94%]
Analysis\test_resolutions.py .                                                                                                                                                                                               [ 94%]
Analysis\test_scattering.py ....                                                                                                                                                                                             [ 95%]
Analysis\test_thermodynamics.py .......                                                                                                                                                                                      [ 96%]
NeutronInstrument\test_instrument.py .                                                                                                                                                                                       [ 97%]
molecules\test_chemistry.py ..x                                                                                                                                                                                              [ 97%]
molecules\test_connectivity.py ......                                                                                                                                                                                        [ 99%]
molecules\test_rdkit.py ....                                                                                                                                                                                                 [100%]

================================================================================================= 434 passed, 1 xfailed in 43.78s =================================================================================================

[MBartkowiakSTFC]

I had a closer look at this part since the expected result has changed in this one, but it is clear that the new values are correct.

[MBartkowiakSTFC]

All the tests that were supposed to pass really pass. Thank you working on it. The changes can be merged.