fs: support utimes BigInt

What is the problem this feature will solve?

Current utimes FS functions have a granularity of microseconds, while the stats BigInt functionality has a granularity of nanoseconds.

What is the feature you are proposing to solve the problem?

Adding support for BigInt to the utimes functions to enable nanosecond granularity for setting timestamps.

What alternatives have you considered?

The underlying reason for this issue is that floating point second values only have 24 significant digits, which does not extend to exact nanoseconds. Having stats support BigInt u64 times, while having utimes not creates the inability to exactly set and read the same level of precision. Relying on a BigInt input as a u64 nanoseconds value seems the most sensible way to resolve this to me.

まず、filesystem の utimes 関数と既存の stats の BigInt 機能を特定します。それぞれがタイムスタンプの精度をどのように表現しているかを比較し、関連するプラットフォーム固有のパスを特定します。BigInt 入力でナノ秒精度のタイムスタンプを設定でき、それらの値を一致する精度で読み戻せれば完了です。