Make sure all BIGNUM operations work within the FIPS provider

Make sure all BIGNUM operations work within the FIPS provider

The FIPS provider does not have a default OPENSSL_CTX so, where
necessary, we need to ensure we can always access an explicit
OPENSSL_CTX. We remove functions from the FIPS provider that use
the default OPENSSL_CTX, and fixup some places which were using
those removed functions.

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9310)