This patch adds MAC address support for EthernetNetworkSpecifier under
@hide flag.
After adding the support, EthernetNetworkSpecifier will be able to be
matched by MAC address in addition to existing interface name match. The
specifier can be satisfied with either MAC address and/or interface
name.
Bug: 397536853
Test: atest CtsNetTestCases:android.net.cts.EthernetNetworkSpecifierTest
Flag: EXEMPT mainline
Change-Id: Ibe55411ad0d3fdded6e25c9f33d9898e3eab3a3c
4259f55ef1