Implementation of Eth Connect & Disconnect Network am: c3bfad406f am: 901a2c6394 am: b62b8b27d7 am: eabb014e1f

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

Change-Id: I6f852bcc8b9d43a734873812961c5954f0f09d72
tree: 51e17e5afa62e998e1c079e3d9f77aa0aa126590
  1. service-t/
  2. tests/