Improve Geometry class

[yguclu]

• Add new factory class method from_file
• Use __init__ method in all factory class methods (from_file, from_discrete_mapping, and from_topological_domain)
• Discourage direct use of __init__ (factory class methods should be preferred)
• Add mandatory pdim parameter (number of dimensions of physical domain) to __init__
• Clean up and document (with docstrings) the factory class methods
• Add Pytest mark @pytest.mark.xdist_group('h5py') to all tests in psydac.cad.tests.test_geometry, because h5py is not thread-safe

Moreover:

• Use SymPDE version 0.20.0
• Always provide interface orientation to the join constructor of Domain objects (from sympde.topology.domain)
• Add interface orientation to multipatch geometry files (in the folder psydac/cad/mesh/multipatch)
• Use ubuntu_installations action in documentation workflow

TO DO:

• In from_file, make sure that the domain argument (an instance of sympde.topology.Domain) is compatible with the topological domain defined in the .yml section of the HDF5 file.
• Update unit tests in cad.tests.test_geometry:
  • Add some 1D unit tests
  • Add proper asserts statements to test_geometry_2d_1 and test_geometry_2d_2
  • Remove obsolete test function test_geometry_1
  • Test functions from cad.cad in new module cad.tests.test_cad
• After release of SymPDE version 0.20.0, update pyproject.toml and run all unit tests once again on all platforms
• Mention SymPDE 0.20.0 in PR description
• Mention SymPDE 0.20.0 in CHANGELOG.md
• Reactivate unit tests on all Python versions