Launch modes settings from empty shade view

When modes are blocking notifications in the shade, launch the
corresponding modes setting when pressing on the text. If only one mode
is blocking notifications, launch that specific mode's settings page. If
multiple modes are blocking notifications, launch the general Modes
settings page.

In order to do this nicely, I am replacing
NotificationActivityStarter#startHistoryIntent with a more generic
NotificationActivityStarter#startSettingsIntent. Also using the same
approach for the FooterView for consistency, as this would allow us to
also launch other things from there in the future. Another benefit is
also that it allows us to test this logic (since it's in the viewModel
instead of the binder now).

Bug: 366003631
Test: manually tested that the intents are launched correctly (and the
back stack is correct) + viewmodel unit tests
Flag: android.app.modes_ui_empty_shade

Change-Id: I3c0f9e9109c6a007749e12be95f5f858388d04a5