Merge branch 'netlink-specs-rtnetlink-adjust-specs-for-c-codegen'

Jakub Kicinski says:

====================
netlink: specs: rtnetlink: adjust specs for C codegen

The first patch brings a schema extension allowing specifying
"header" (as in .h file) properties in attribute sets.
This is used for rare cases where we carry attributes from
another family in a nest - we need to include the extra
headers. If we were to generate kernel code we'd also
need to skip it in the uAPI output.

The remaining 11 patches are pretty boring schema adjustments.
====================

Link: https://patch.msgid.link/20250418021706.1967583-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>