Implement the new added EthernetManager APIs. am: b8ab4c869f

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/1968579

Change-Id: I3aa995605defb39d45e7c4ed2accdde4b87fa452
tree: d9d9b53a8d6cc752d5463b533407dfc70b77d53c
  1. service-t/
  2. tests/