Promote SSL_get_negotiated_group() for non-TLSv1.3

Promote SSL_get_negotiated_group() for non-TLSv1.3

It can be useful to know what group was used for the handshake's
key exchange process even on non-TLS 1.3 connections.  Allow this
API, new in OpenSSL 3.0.0, to be used on other TLS versions as well.
Since pre-TLS-1.3 key exchange occurs only on full handshakes, this
necessitates adding a field to the SSL_SESSION object to carry the
group information across resumptions.  The key exchange group in the
SSL_SESSION can also be relevant in TLS 1.3 when the resumption handshake
uses the "psk_ke" key-exchange mode, so also track whether a fresh key
exchange was done for TLS 1.3.

Since the new field is optional in the ASN.1 sense, there is no need
to increment SSL_SESSION_ASN1_VERSION (which incurs strong incompatibility
churn).

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14750)