Further tidy up cipher logic.

With SSL2 gone, there's no need for this split between the abstract
cipher framework and ciphers. Put the cipher suite table in ssl_cipher.c
and move other SSL_CIPHER logic there. With that gone, prune the
cipher-related hooks in SSL_PROTOCOL_METHOD.

BUG=468889

Change-Id: I48579de8bc4c0ea52781ba1b7b57bc5b4919d21c
Reviewed-on: https://boringssl-review.googlesource.com/4961
Reviewed-by: Adam Langley <agl@google.com>