Merge branch 'tcp_metrics-netlink-specs' into main

Jakub Kicinski says:

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tcp_metrics: add netlink protocol spec in YAML

Add a netlink protocol spec for the tcp_metrics generic netlink family.
First patch adjusts the uAPI header guards to make it easier to build
tools/ with non-system headers.

v1: https://lore.kernel.org/all/20240626201133.2572487-1-kuba@kernel.org
====================

Signed-off-by: David S. Miller <davem@davemloft.net>