fix(divan): use busy sleep in time scale examples

[GuillaumeLagrange]

For these times, using thread::sleep makes no sense as, at least on linux, the scheduler's timer resolution is orders of magnitude larger than nanoseconds.

[codspeed-hq]

CodSpeed Performance Report

Merging #149 will degrade performances by 10%

_{Comparing fix/busy-sleep-time-scale-benches (e5436a5) with main (550d10f)}

Summary

⚡ 5 improvements
❌ 1 regression
✅ 360 untouched

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Mode	Benchmark	BASE	HEAD	Change
❌	WallTime	iter_batched_ref_per_iteration	36 ns	40 ns	-10%
⚡	WallTime	from_elem[8192]	544 ns	507 ns	+7.3%
⚡	WallTime	from_elem_decimal[2048]	264 ns	252 ns	+4.76%
⚡	WallTime	sleep_100ns	62,315 ns	194 ns	×320
⚡	WallTime	sleep_100us	162.2 µs	100.1 µs	+62.02%
⚡	WallTime	sleep_1us	63.3 µs	1.1 µs	×58