More EVP ECC testing: positive and negative

1. For every named curve, two "golden" keypair positive tests.
2. Also two "golden" stock ECDH positive tests.
3. For named curves with non-trivial cofactors, additionally two "golden"
   ECC CDH positive tests.
4. For named curves with non-trivial cofactors, additionally two negative
   tests.

There is some overlap with existing EVP tests, especially for the NIST
curves (for example, positive testing ECC CDH KATs for NIST curves).

"Golden" here means all the values are independent from OpenSSL's ECC
code. I used sage to calculate them. What comes from OpenSSL is:

1. The OIDs (parsed by tooling)
2. The curve parameters (parsing ecparam output with tooling)

The values inside the PEMs (private keys, public keys) and shared keys
are from sage. The PEMs themselves are the output of asn1parse, with
input taken from sage.

Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6608)