Passing meta/action key related key events when private flag is set

New private flag: PRIVATE_FLAG_INTERCEPT_KEYBOARD_SHORTCUTS
Window using it also needs to have permission OVERRIDE_SYSTEM_KEY_BEHAVIOR_IN_FOCUSED_WINDOW
in order to receive key events containing meta/action key

Test: add private flag and permission and see key events received in
focused window
Test: PhoneWindowManagerTests
Flag: EXEMPT usage of private flag is flagged in SysUI with com.android.systemui.shared.new_touchpad_gestures_tutorial
Bug: 358587037

Change-Id: I0ad1b838c5a9e2bbe71198950ddb23ea92b2cd47