Add getInterfaceList API implementation in Ethernet service. am: 6e44855f90 am: 6c3b9485d9

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/2029725

Change-Id: I7cb7ee51f75f84a969eb8b9fb09755de544ce685
tree: 3f5d28165188047b66b9fbad64822b9e648fd32c
  1. service-t/
  2. tests/