core: Generate/parse filetime info

[antangelo]

Currently, the filetime field within the volume descriptor is printed as-is as a u64, and is generated as zero. We should be able to generate and view the filetime info in a better format.

Note that this will require special care on the web, as typical interfaces for determining time do not work in browser.

See https://learn.microsoft.com/en-us/windows/win32/sysinfo/file-times for format