Replace INetd#trafficSwapActiveStatsMap with ConnectivityManager API

INetd#trafficSwapActiveStatsMap is deprecated and the implementaion is
moved into tethering (connectivity) mainline module. A new
ConnectivityManager API swapActiveStatsMap is temprary exposed for
NetworkStatsFactory. Once NetworkStatsFactory move into tethering
module, swapActiveStatsMap API would be removed and NetworkStatsFactory
should could call the implemeneted inside the module directly. This
should happen before T sdk finalization.

Bug: 209935649
Test: atest NetworkStatsFactoryTest
Change-Id: I6685fe513511e7af9fa6521601891c66d1297da0