Add translation for ECX group parameter

Add translation for ECX group parameter

Legacy EVP_PKEY_CTX objects did not support the "group" parameter for X25519
and X448.  The translation of this parameter resulted in an error.  This
caused errors for legacy keys and engines.

Fix this situation by adding a translation that simply checks that the correct
parameter is to be set, but does not actually set anything.  This is correct
since the group name is anyway optional for these two curves.

Fixes #19313

Signed-off-by: Juergen Christ <jchrist@linux.ibm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19348)