Ethernet framework and service source code is going to be moved to
Connectivity mainline module, this CL contains below corresponding
changes to adapt the migration in f/b side:
1. Split out ethernet module-lib APIs to Connectivity module.
Add the ethernet resource filegroup to tiramisu-updatable-sources
filegroup as well, build them together. Also update the module-lib
and system api txt to reflect the APIs change. Remove the hidden
APIs which are moved to Connectivity module. This removal fixes the
api inconsistent issue with Tethering/apex/hidden/.
2. Remove EthernetService from SystemServer which will be registered
from ConnectivityServiceInitializer.
3. Replace the BackgroundThread class(imported from f/b/core/java)
with the one in the modules-utils-backgroundthread lib, which is
visible to Connectivity module.
Bug: 210586283
Test: m
Test: atest FrameworksNetTests EthernetServiceTests
Change-Id: I1956848d3248cc56e9841d221e5e4c160bed65a4
218c4d3162