Merge branch 'fix-netdevim-to-correctly-mark-napi-ids'

Joe Damato says:

====================
Fix netdevim to correctly mark NAPI IDs

This series fixes netdevsim to correctly set the NAPI ID on the skb.
This is helpful for writing tests around features that use
SO_INCOMING_NAPI_ID.

In addition to the netdevsim fix in patch 1, patches 2 & 3 do some self
test refactoring and add a test for NAPI IDs. The test itself (patch 3)
introduces a C helper because apparently python doesn't have
socket.SO_INCOMING_NAPI_ID.

v3: https://lore.kernel.org/20250418013719.12094-1-jdamato@fastly.com
v2: https://lore.kernel.org/20250417013301.39228-1-jdamato@fastly.com
rfcv1: https://lore.kernel.org/20250329000030.39543-1-jdamato@fastly.com
====================

Link: https://patch.msgid.link/20250424002746.16891-1-jdamato@fastly.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>