Fix memory leak in EVP_PKEY_get1_encoded_public_key.

Fix memory leak in EVP_PKEY_get1_encoded_public_key.

Occurs if a failure happens after the malloc call in the second call to
EVP_PKEY_get_octet_string_param().

Detected by PR #18355

Some calling code assumes that nothing is allocated in the returned
pointer if there was a failure. Other calling code always trys freeing.
The third case is in ecdh_cms_encrypt() where it does not check the
return value. I am assuming this change is ok since the legacy path in
EVP_PKEY_get1_encoded_public_key() also does not return the pointer on
failure.

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18739)