Stylus shouldnt trigger gestures during handwriting

Exclude navbar from stylus gesture when handwriting is in progress.
Layer the input consumer surface for handwriting above so that stylus
touches dont go to gesture navbar or 3-botton navbar while handwriting
is ongoing.
User can still swip to home with finger.

Fix: 240451878
Test: atest StylusHandwritingTest
   and Manually:
   1. build & flash
   2. start a handwriting session
   3. while session is inprogress, attempt to swipe to home with stylus
   4. gesture shouldn't work.
   5. Repeat same with finger and it should work.
Change-Id: I5c7194d45beb4ba0a0f629f3860fc713270815f1