selftests: drv-net: psp: add connection breaking tests

Add test checking conditions which lead to connections breaking.
Using bad key or connection gets stuck if device key is rotated
twice.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Link: https://patch.msgid.link/20250927225420.1443468-7-kuba@kernel.org


Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>