Add differential fuzz tests for libcrypto crypto

[goatgoose]

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Problem:

#4020 adds the libcrypto TLS PRF implementation to s2n-tls, which is used in some scenarios rather than the custom s2n-tls implementation. The PRF unit tests contain known-value tests that ensure both the TLS and libcrypto implementations are correct. However, now that two different implementations exist, we should additionally add a fuzz test that provides both versions a bunch of random input and makes sure they produce the same results.

The same should also be done for HKDF after it's added, and also HMAC potentially.