selftests: net: py: read ip link info about remote dev

selftests: net: py: read ip link info about remote dev

We're already saving the info about the local dev in env.dev
for the tests, save remote dev as well. This is more symmetric,
env generally provides the same info for local and remote end.

While at it make sure that we reliably get the detailed info
about the local dev. nsim used to read the dev info without -d.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20251120021024.2944527-8-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>