feat: Indicate that md5 is used as a CRC

MD5 in storage helpers is used as a CRC function for
non-cryptographically secure purposes. Ensure that md5 is initiated
with `usedforsecurity=False` to ensure that Python in FIPS mode can
fetch MD5 implementation for such non cryptographically secure
purpose.

This is no effective change on non-FIPS mode Python installations.

This improves compatibility with most FIPS mode Python installations.

Author: xnox

google/cloud/storage/_helpers.py

@@ -536,7 +536,7 @@ def _base64_md5hash(buffer_object):
     :rtype: str
     :returns: A base64 encoded digest of the MD5 hash.
     """
-    hash_obj = md5()
+    hash_obj = md5(usedforsecurity=False)
     _write_buffer_to_hash(buffer_object, hash_obj)
     digest_bytes = hash_obj.digest()
     return base64.b64encode(digest_bytes)