RAND_DRBG: add a callback data for entropy and nonce callbacks

RAND_DRBG: add a callback data for entropy and nonce callbacks

The callback data allows passing context specific data from the
application of the DRBG to to the entropy callbacks.
This a rather specialized feature which is useful for implementing
known answer tests (KATs) or deterministic signatures (RFC6979),
which require passing a specified entropy and nonce for instantiating
the DRBG.

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/10950)