Implementation of Eth Connect & Disconnect Network am: c3bfad406f am: 901a2c6394

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/1955448

Change-Id: I0cc1793b75f4aa7fb480f1a5277dcdb774a41e64
tree: 51e17e5afa62e998e1c079e3d9f77aa0aa126590
  1. service-t/
  2. tests/