Merge branch 'selftest-netconsole-enhance-selftest-to-validate-userdata-transmission'

Breno Leitao says:

====================
selftest: netconsole: Enhance selftest to validate userdata transmission

The netconsole selftest has been extended to cover userdata, a
significant subsystem within netconsole. This patch introduces support
for testing userdata by appending a key-value pair and verifying its
successful transmission via netconsole/netpoll.

Additionally, this patchseries addresses a pending change in the subnet
configuration for the selftest.

v1: https://lore.kernel.org/20241025161415.238215-1-leitao@debian.org
====================

Link: https://patch.msgid.link/20241029090030.1793551-1-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>