Give touch boost higher priority than idle detection

When the non-kernel idle timer is used, touch boost wasn't being applied
when the device was idle. I moved the code around to ensure touch boost
is applied when the device is idle.

Bug: 154571341

Test: - Wrote a new unit test to confirm correct idle behavior.
      - Locally modified a Pixel 4 to use the regular idle timer rather
        than the kernel idle timer, and confirmed we now apply touch
        boost correctly.

Change-Id: Id998405a4d79f7a89fc0523b6503fe1a3dea8cce