[roll] Roll fuchsia [network-test-realm] Close device session on the system netstack

Before this change, network-test-realm only disables the interface on
the system netstack and left the session open, this is our last use
case of multi-session support in network device. This interface is
never intended to be used on the system netstack, we should close
the session which will in turn trigger the removal of all interfaces
that is backed by the session. An API is added to fuchsia.net.debug
to support this feature, because this is only intended to be used
for tests.

As a side effect, because the interface will no longer exist on the
system netstack, we need a different way for `add_interface` to find
the backing network-device, service capability is used for this.

We no longer attempt to restore the system netstack to the same as
before, it is unnecessary because a test interface is not supposed
to have "real" traffic even after the test stops. We don't have any
guarantee for the recover either before the change - if the test
crashes, we were only trying our best to reenable the interface, and
it may remain disabled.

Original-Bug: 504643320
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1578516
Original-Revision: 1f07def38761a23a510ac6a8a8c83f5545d4fa51
GitOrigin-RevId: 7eaeeb0573e6c253755ec40d0f9a8ad13db15283
Change-Id: Ifdc5faabb8fd2ba5d0687e17ebb08a95346aaf6b