Implement os.setns, os.unshare to allow changing namespaces in Linux

As for now, changing to a different namespace is really messy, one must use ctypes, and call libc functions to do so.
I think implementing setns and unshare functions will make working with namespaces in Python much easier

pythongh-95023: added os.setns and os.unshare for namespaces switchin…

gh-95023: Added os.setns and os.unshare functions (#95046)