Add additional ECDSA/Ed25519 selection tests.

Add two tests with ECDSA+SHA256 preferred over Ed25519, the second also
excludes P-256 from the supported curves extension which will force the
use of Ed25519 in TLS 1.2, but not TLS 1.3: this would fail before the
certificate table updates.

Add TLS 1.3 test also with P-256 exclude from the groups extension: this
should have no effect as the groups extension is not used for signature
selection in TLS 1.3

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3858)