We prevent a lot of tests from getting run on tools/ changes given
that most of that is unrelated to running any tests. By having the
gate hooks in that directory it made for somewhat odd separation of
what is test sensitive and what is not.
This moves things to the gate/ top level directory, and puts a symlink
in place to handle project-config compatibility until that can be
updated.
Change-Id: Iec9e89f0380256c1ae8df2d19c547d67bbdebd65
95441ef896