ethernet: add test for updateConfiguration on untracked interface

The automotive team has confirmed that updating IpConfiguration /
NetworkCapabilities should succeed independent of the interface state
(absent, client mode, server mode). This ensures updateConfiguration
works when the interface is absent, and the configuration is applied to
the interface once it gets added.

Test: atest EthernetManagerTest --iterations 10
Bug: 236312641
Change-Id: I6d295bce4575daca2061f46313732a9e4600a2ee