Add a new keycode for TV (ALL_APPS)

    - KEYCODE_ALL_APPS: Launches all apps. For TV, this checks for
      launcher package in system image.

Test: Manual: ALL_APPS: adb shell input keyevent 284
Test: also tested with --longpress for these keys

Bug: 38496261
Change-Id: I2e50a569533f01d93c020adde672c842540f0193