Add benchmarks for EC_KEY_generate_key(_fips)

[samuel40791765]

Description of changes:

While working on #957, we noticed that we could use some benchmarks for EC_KEY_generate_key(_fips) as well.

Call-outs:

N/A

Testing:

N/A

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and
the ISC license.

[dkostic]

what's the difference between the existing SpeedECKeyGenCurve and your new SpeedECKeyGenerateKey?

[samuel40791765]

what's the difference between the existing SpeedECKeyGenCurve and your new SpeedECKeyGenerateKey?

The existing SpeedECKeyGenCurve used EVP_PKEY_CTX and called EVP_PKEY_keygen to generate the key. We were missing comparisons between EC_KEY_generate_key vs EC_KEY_generate_key_fips, so we decided to add them.

More context: #957 (comment)