Support FFDHE groups in tls1_shared_group

Support FFDHE groups in tls1_shared_group

Update tls1_shared_group to allow filtering for FFDHE and/or ECDHE
groups. This will be used for implementing RFC 7919 groups support in
the TLS 1.2 server. As defined in RFC 7919:
   Codepoints in the "Supported Groups Registry" with a high byte of
   0x01 (that is, between 256 and 511, inclusive) are set aside for
   FFDHE groups

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
MergeDate: Thu Feb  5 09:09:38 2026
(Merged from https://github.com/openssl/openssl/pull/24551)