Next (simplified setup.py interface to run SWIG, rolled back METIS version, and rolled back default MFEM version)

[sshiraiwa]

This PR follows up PR #143. This includes changes in setup.py so that

• Run SWIG generator automatically in all cases (An "important" side effects: A user needs to have SWIG installed. pip install swig)
• Roll back how METIS build is handled. It uses tar.gz in mfem/tpls.
• Delete .py/.h/.cxx files which are generated by SWIG.
• Roll back the default install MFEM version to 4.4.0 (SHA = a1f6902ed72552f3e680d1489f1aa6ade2e0d3b2)

TODO:

• Adjust github actions in master to test it properly.

[sshiraiwa]

This PR should fix the issue discussed in #141 and #144