ci: Add Python 3.13 to ci/cd workflows

[mhoeijm]

Issues for Python 3.13 compatibility:

• Requires VTK 9.5 support

Tests seem to fail due to dependency conflicts

• CI/CD succeeds: Python==3.12: pyvista==0.45.3 and vtk==9.3.1
• CI/CD fails: Python==3.13: pyvista==0.44.1 and vtk==9.5

The conflict is caused by:
    The user requested vtk!=9.4.*, <9.6 and >=9.1.0
    pyvista 0.45.3 depends on vtk!=9.4.0
    pyvista 0.45.3 depends on vtk!=9.4.1
    pyvista 0.45.3 depends on vtk<9.5.0

With pyvista==0.46 we need to get rid of the main_has_priority flag:

 E               ValueError: The keyword 'main_has_priority' is deprecated and should not be used.
E               The main mesh will always have priority in a future version, and this keyword will be removed.
E               Its value cannot be False for vtk>=9.5.0.