Merge branch 'tools-ynl-generate-code-for-the-handshake-family'

Jakub Kicinski says:

====================
tools: ynl: generate code for the handshake family

Add necessary features and generate user space C code for serializing
/ deserializing messages of the handshake family.

In addition to basics already present in netdev and fou, handshake
has nested attrs and multi-attr u32.
====================

Link: https://lore.kernel.org/r/20230606194302.919343-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>