CryptoPkg/BaseCryptLib: avoid using SHA256()

In openssl 3.0 SHA256() goes through the provider logic,
requiring a huge amount of openssl code.  The individual
functions do not, so use them instead.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>