Fix bugs in ECDH cofactor FIPS indicator.

Fix bugs in ECDH cofactor FIPS indicator.

The code was not detecting that the cofactor was set up correctly
if OSSL_PKEY_PARAM_USE_COFACTOR_ECDH was set, resulting in an incorrect
FIPS indicator error being triggered.

Added a test for all possible combinations of a EVP_PKEY setting
OSSL_PKEY_PARAM_USE_COFACTOR_ECDH and the derive context setting
OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE.

This only affects the B & K curves (which have a cofactor that is not 1).

Bug reported by @abkarcher

Testing this properly, also detected a memory leak of privk when the
FIPS indicator error was triggered (in the case where mode = 0 and
use_cofactor was 1).

Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/25548)

(cherry picked from commit 2f362e99a1178263c7102474f0190836166f416d)