Split out the connectivity API surface

Split out connectivity APIs to connectivity module directories. This
prepares future move of the connectivity code into a mainline module,
but still keeps it implemented by framework-minus-apex for now: the API
stubs are moved to framework-connectivity.stubs, but the implementation
on device remains in the same place.

This allows moving the connectivity code in/out of APEX with minimal
changes.

BYPASS_INCLUSIVE_LANGUAGE_REASON=Moving files, can't modify released API

Bug: 171540887
Test: device boots, connectivity working

Change-Id: I21c42f032efa6c10e36c749df3183ce9679303a7