Function reset_shrink_progress 

pub(crate) fn reset_shrink_progress(
    config: &InvariantConfig,
    progress: Option<&ProgressBar>,
    label: &str,
    position: Option<(usize, usize)>,
)

Resets the progress bar before each shrink. position = Some((i, N)) renders [i/N] Shrink: <label> for multi-invariant campaigns.