FileManager should use utimensat instead of utimes

[jakepetroules]

utimensat has nanosecond precision, while utimes only has microsecond precision. At least APFS should be able to take advantage of the elevated precision.

[jmschonfeld]

Reopening as the change was reverted in #1379. This ability is blocked on the ability for Date to represent times with nanosecond precision since this FileManager API uses Date as the currency type