Fix map drag detection bug

[afarber]

Fix bug where map dragging was incorrectly registered as clicks in Android Automotive emulator.

Problem

During map dragging, the movement distance calculation in ACTION_UP was measuring from the last ACTION_MOVE position instead of the initial ACTION_DOWN position. This
caused long drags to be misinterpreted as clicks.

Solution

• Add initialTouchX and initialTouchY fields to OpenMapView.kt to capture the initial touch position in ACTION_DOWN handler
• Change click detection in ACTION_UP to use initial position instead of last position
• Add instrumentation tests (TouchGestureInstrumentationTest.kt) to verify:
  • Long drags (200px) are NOT registered as clicks
  • Small movements (3px) ARE registered as clicks