Move the rand_nonce_lock code into drbg_lib.c

It was previously rand_lib but it makes more sense in drbg_lib.c since
all the functions that use this lock are only ever called from drbg_lib.c

We add some FIPS_MODE defines in preparation for later moving this code
into the FIPS module.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9039)