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.

Empieza localizando las funciones utimes del sistema de archivos y la funcionalidad BigInt existente de stats. Compara cómo representa cada una la precisión de las marcas de tiempo e identifica las rutas relevantes específicas de cada plataforma. Se considera terminado cuando las entradas BigInt pueden establecer marcas de tiempo con precisión de nanosegundos y esos valores se pueden volver a leer con la misma precisión.