Add test case for ModifierShortcutManager

Ensure that shift based app launch shortcuts are covered by tests.
Also:
 - Update bookmark shortcut key from A to J to not intefere with
   system wide meta+a shortcut
 - Remove unused PackageManager mocking in TestPhoneWindowManager
   the throw on any input means we can't otherwise mock the method.

Bug: 351963350
Test: atest ModifierShortcutManagerTests ModifierShortcutTests
Flag: TEST_ONLY

Change-Id: Ie858365b1a24537ce7693f71ec42508c2cbdeeee