fw/b: Add support for allowing/disallowing apps on cellular, vpn and wifi networks

* Dynamically add/remove apps from restricted networking mode's allowlist based on policy and network transport changes
* Listen to changes in all networks
* Limit backend calls during network capability changes to transport changes
* Allow traffic over VPN networks if policy does not restrict it even if other transports are present

Original-Change-Id: I526d0058cda71a9e93046d116c0d79093390a85b
Original-Change-Id: I0d719bb7c7f04a493a4ddefa8e6154ef4159abd0
Change-Id: I48e08f34ebc62d90e13bd2f4bd19423dbd168039