wireguard: uapi: generate header with ynl-gen

wireguard: uapi: generate header with ynl-gen

Use ynl-gen to generate the UAPI header for WireGuard.

The cosmetic changes in this patch confirms that the spec is aligned
with the implementation. By using the generated version, it ensures
that they stay in sync.

Changes in the generated header:
* Trivial header guard rename.
* Trivial white space changes.
* Trivial comment changes.
* Precompute bitflags in ynl-gen (see [1]).
* Drop __*_F_ALL constants (see [1]).

[1] https://lore.kernel.org/r/20251014123201.6ecfd146@kernel.org/

No behavioural changes intended.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>