rgw/d4n: squashing commits related to changing

rgw/d4n: squashing commits related to changing
creationTime type from time_t to double.

1. rgw/d4n: Change score calculation
2. rgw/d4n: Update creationTime calculation to include decimal value
3. rgw/d4n: changes for converting string value to
time_point, when creationTime type changed to double.

Co-authored-by: Pritha Srivastava <prsrivas@redhat.com>
Updated bucket::list to convert from string to time_point

Signed-off-by: Samarah <samarah.uriarte@ibm.com>
Signed-off-by: Pritha Srivastava <prsrivas@redhat.com>