CORE-5042 Refactored stat endpoint response formats.

Added id and path fields, and updated size/created/modified to file-size/date-created/date-modified to be consistent with other listing endpoints.
Updated the date-created and date-modified fields to just longs rather than strings.
CORE-5042 Updated file-size in listings/sub-file-maps.

Changed file-size to a long rather than a string for consistency with other endpoints.