Allow gesture shortcut to be clickable while FAB is present.

Changes the conditions for enabling press/long press shortcuts.
The shortcuts should be active if the a11y button mode is set to navbar,
or if there are any gesture shortcut targets.
These conditions allow for gesture to be enabled at the same time as the FAB.

(Note: it's still not possible to perform a gesture shortcut using gesture targets
- the gesture input needs to be told to use the proper targets first)

Test: atest NavBarHelperTest NavigationBarTest
Flag: android.providers.a11y_standalone_gesture_enabled
Bug: 300313558
Change-Id: Iab948bad722c4fceb48f6dd9d909306babfb2170