Replace perform-release.sh with perform-release.py

I discovered a bug in perform-release.sh where it sets up a trap to "rm -fr $TMP" inside of a function, but TMP is local to the function, so it has no value if the trap fires after the function has exited (which is the normal case). This triggered me to rewrite the the code in Python which has proper finalizers. That said, using Python removes the need to write use temporary files in the first place.

Change-Id: Ibcf075b42c502d8b76e113c9a9c28f783aa82157