z3: bugfix about python dependency and fallthrough annotation. (#13713)

* z3:

* Fixed python dependency to always be required.

* bugfix about fallthrough annotation.

* z3: Add patch for before ver.4.4.1.

* Update var/spack/repos/builtin/packages/z3/package.py

Co-Authored-By: Adam J. Stewart <ajstewart426@gmail.com>