Implementation of Eth Connect & Disconnect Network am: c3bfad406f am: 901a2c6394 am: b62b8b27d7

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

Change-Id: I1e7fc5929b9104b6b607adaf5d84dbd8122642f4
tree: 51e17e5afa62e998e1c079e3d9f77aa0aa126590
  1. service-t/
  2. tests/