Add the FIPS related continuous random number generator (CRNG) testing.

Refer to FIPS 140-2 section 4.9.2 Conditional Tests for details.

The check is fairly simplistic, being for the entropy sources to not feed
the DRBG the same block of seed material twice in a row.  Only the first
DRBG in a chain is subject to this check, latter DRBGs are assumed to be
safely seeded via the earlier DRBGs.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8599)