ssl/statem: write 16-bit ECDHE group id in SKE

ssl/statem: write 16-bit ECDHE group id in SKE

tls_construct_server_key_exchange wrote the named group as two u8 bytes with the high byte set to 0. TLS requires a 16-bit NamedGroup. Use WPACKET_put_bytes_u16(curve_id) so ids >= 256 are encoded correctly. No change for groups < 256.

Signed-off-by: Joshua Rogers <MegaManSec@users.noreply.github.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28835)