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

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

Change-Id: Id8eba7b7f968c04f233fe8e3629a236aab9e2bc9
tree: 3f5d28165188047b66b9fbad64822b9e648fd32c
  1. service-t/
  2. tests/