fs: add Temporal.Instant support to Stats and BigIntStats

[LiviaMedeiros]

Refs: #57891

This is a very rough draft, and probably shouldn't land until Temporal implementation is finalized and/or enabled by default.
Opening early to see if there are any objections, suggestions to naming (the *Instant properties are facing userspace and having consistent convention would be nice), or to implementation.

[Renegade334]

Since Date.prototype.toInstant() comes along with Temporal, these are fairly trivial to obtain anyway? (Although come to think of it, this would lose nanosecond precision.)

It might be better to have this as a switchable option similar to bigint, rather than adding the overhead of building a load of Temporal objects for every stats call?

[LiviaMedeiros]

Since Date.prototype.toInstant() comes along with Temporal, these are fairly trivial to obtain anyway?

Converting from Date would have performance overhead on top of precision loss.

It might be better to have this as a switchable option similar to bigint, rather than adding the overhead of building a load of Temporal objects for every stats call?

These properties are lazy-loaded, so the overhead when not used should be minimal.

[aduh95]

We're probably going to want to support building node without Temporal support for a while

Suggested change

	// TODO(LiviaMedeiros): TemporalInstant primordial
	return new Temporal.Instant(BigInt(MathFloor(msec / kMsPerSec)) * kNsPerSecBigInt + BigInt(nsec));
	if (Temporal == null) throw 'informative error';
	// TODO(LiviaMedeiros): TemporalInstant primordial
	return new Temporal.Instant(BigInt(MathFloor(msec / kMsPerSec)) * kNsPerSecBigInt + BigInt(nsec));

[LiviaMedeiros]

Agreed, especially with mandatory Rust requirements.
Added the error, the message text is subject to changes (if this may land before enabling Temporal by default, it should also suggest --harmony-temporal flag)

[aduh95]

Suggested change

	ObjectDefineProperty(this, 'atimeInstant', { __proto__: null, value, writable: true });
	setOwnProperty(this, 'atimeInstant', value);

[LiviaMedeiros]

AFAICT this will make the property enumerable, even though the initial getter is not? I don't mind it, but this better be aligned with how Date setters behave.

[aduh95]

We should probably add an additional optional enumerable argument to setOwnProperty