selftests: drv-net: rss_input_xfrm: Check test prerequisites before running

Ensure the following prerequisites before executing the test:
1. 'socat' is installed on the remote host.
2. Python version supports socket.SO_INCOMING_CPU (available since v3.11).

Skip the test if either prerequisite is not met.

Reviewed-by: Nimrod Oren <noren@nvidia.com>
Signed-off-by: Gal Pressman <gal@nvidia.com>
Link: https://patch.msgid.link/20250430054801.750646-1-gal@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>