Move ApfFilter from ConnectivityService to IpManager

There's a few advantages to having ApfFilter in IpManager:
1. If things go wrong, crashing a particular transport is less bad then
   crashing ConnectivityService.  We also don't want to use
   ConnectivityService as a dumping ground for transport-specific logic.
2. This makes implementing WifiManager.MulticastLock a lot simpler and
   safer because enabling/disabling it doesn't have to go through the
   NetworkAgent, which could risk various races (e.g. installing a filter
   into the wrong WiFi network).
3. IpManager is the ultimate source for LinkProperties for a particular
   transport and since ApfFilter uses the LinkProperties it's better to
   have it closely paired with the IpManager. Likewise, ApfFilter needs
   to know the APF capabilities of the transport, so having it in
   the transport avoids having to parcel this information through the
   NetworkAgent.

Bug: 26238573
Change-Id: I99b85f2b64972f0e7572170ec5d1926081aa3429