Function format_elapsed 

pub fn format_elapsed(duration: Duration) -> String

Format a Duration as a human-readable string.

Returns milliseconds for durations under 1 second, otherwise seconds with 3 decimal places.

use rusty_stack::installers::common::benchmark_common::format_elapsed;
use std::time::Duration;

assert_eq!(format_elapsed(Duration::from_millis(500)), "500ms");
assert_eq!(format_elapsed(Duration::from_millis(1500)), "1.500s");