Delete bpt

This project hasn't been in our manifest in a long time, and
the only usage of bpttool we had was deleted in aosp/2654584.

A partner was asking about this repository, so detete it just to clear
up any confusion.

The tool is also written in python 2, which we want to remove.

Test: Presubmits
Change-Id: Ibb4d38b3e0661f787096d07924f929174cddd41b