Refactor emulator buildbot
Create builers in multiple categories.
There are quite some changes in this CL,
1. Create categories based on projects, for emulator or system image projects or cross build,
then each builder is created once in each category
2. Trigger builds based on project and category
3. For new builds in emulator branch, run tests against public system images.
Only when it passes, trigger a build on cross builders, to run with
last known good system images builds
4. Similarly, for new build on system image branches, run tests with sdk emulator.
When it passes, trigger a build on cross builders, to run with
last known good emulator build
Change-Id: I28ea308558047edf0058e74aff416f342839dcc3
7 files changed