Move connectivity-sources to frameworks/base

All sources for the connectivity module are being moved to
frameworks/base/packages/Connectivity, so that they can all be moved to
packages/modules/Connectivity in one move keeping history.

INetworkAgent and INetworkAgentRegistry were created in
packages/modules/Connectivity directly, but this makes managing the
sources until the move harder as the module needs to pull sources from
two different locations. Considering that they do not have history to
move, just move them to frameworks/base/packages/Connectivity without
the commit history.

Bug: 171540887
Test: m
Change-Id: Ic4353115a98b6235c2b5d5ce24741223e618d0a6