[Bug Report] `RotatingFileSink` should not truncate on open if rotation policy `FileSize` is used

[SpriteOvO]

This sink truncates log.txt after each construction and does not rotate it.

let file = RotatingFileSink::builder()
    .base_path(dir.join("log.txt"))
    .rotation_policy(RotationPolicy::FileSize(u64::MAX))
    .rotate_on_open(true)
    .build_arc()?;