Implement encoding.BinaryAppender for all CNG-backed crypto hashes

[dagood]

I believe we need to do this here, too:

• https://github.com/golang-fips/openssl/issues/148

[qmuntal]

BCrypt doesn't support getting nor setting the hash inner state, so we can't implement encoding.BinaryAppender. Note that we already don't implement encoding.BinaryMarshaller. Our Go toolchain patches will have to deal with this.