Update desktop gesture exclusion criteria.

Expands the gesture exclusion regions generated per task to include
caption bounds. This prevents gestures from occurring when attempting to
drag position a task from the edge of the screen.

This CL also excludes the corners from the gesture exclusion region for
non-resizeable tasks.

Bug: 296925353
Test: Manual, drag task off the edge of the screen, then drag back from
the edge without triggering gesture.

Change-Id: If6cbcd24934bf0163d226ab5d158c20610f5dde5