Tracking issue for SystemTime accessors from fs::Metadata

[alexcrichton]

This is a tracking issue for three functions added in #30865:

• Metadata::modified
• Metadata::accessed
• Metadata::created

[alexcrichton]

One known FIXME is that resolution of the timestamp is lost on OSX as we convert a timespec to a timeval, converting nanoseconds to microseconds. This probably wants to be fixed at the SystemTime layer which currently uses a timeval representation due to its usage in gettimeofday.

[alexcrichton]

🔔 This issue is now entering its cycle-long final comment period for stabilization 🔔

[alexcrichton]

The libs team discussed this at triage yesterday and the decision was to stabilize