Rollup merge of #76958 - est31:ns, r=oli-obk

Replace manual as_nanos and as_secs_f64 reimplementations

compiler/rustc_data_structures/src/profiling.rs

@@ -600,10 +600,7 @@ pub fn print_time_passes_entry(do_it: bool, what: &str, dur: Duration) {
 // Hack up our own formatting for the duration to make it easier for scripts
 // to parse (always use the same number of decimal places and the same unit).
 pub fn duration_to_secs_str(dur: std::time::Duration) -> String {
-    const NANOS_PER_SEC: f64 = 1_000_000_000.0;
-    let secs = dur.as_secs() as f64 + dur.subsec_nanos() as f64 / NANOS_PER_SEC;
-
-    format!("{:.3}", secs)
+    format!("{:.3}", dur.as_secs_f64())
 }
 
 // Memory reporting