chore: use std::hint::black_box

[DaniPopes]

It has been stable for quite a while now.

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #97 will degrade performances by 18.86%

_{Comparing DaniPopes:std-black-box (1763484) with main (5caa771)}

Summary

❌ 4 regressions
✅ 159 untouched benchmarks

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

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	a	254.7 ns	281.4 ns	-9.48%
❌	a	254.7 ns	281.4 ns	-9.48%
❌	fibo_iterative	126.7 ns	156.1 ns	-18.86%
❌	fibonacci_custom_measurement	916.7 ns	945.8 ns	-3.08%

[codspeed-hq]

CodSpeed Walltime Performance Report

Merging #97 will degrade performances by 87.34%

_{Comparing DaniPopes:std-black-box (1763484) with main (5caa771)}

Summary

⚡ 10 improvements
❌ 6 regressions
✅ 129 untouched benchmarks

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

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	build_vec	212 ns	202 ns	+4.95%
❌	large_drop	169.7 µs	179.2 µs	-5.31%
⚡	large_setup	13 ns	12 ns	+8.33%
⚡	from_elem[2048]	256 ns	236 ns	+8.47%
⚡	from_elem[4096]	332 ns	319 ns	+4.08%
❌	from_elem_decimal[1024]	79 ns	82 ns	-3.66%
⚡	graph_coloring[3]	2.4 µs	1 µs	×2.3
⚡	graph_coloring[6]	4.7 µs	4.4 µs	+7.93%
⚡	rat_in_maze[6]	5.8 µs	3 µs	+95.23%
❌	generate_gray_code[1]	1 µs	2.1 µs	-50%
❌	generate_gray_code[2]	920 ns	3,730 ns	-75.34%
❌	generate_gray_code[3]	455 ns	3,593 ns	-87.34%
❌	generate_gray_code[4]	911 ns	3,572 ns	-74.5%
⚡	instant	5.1 µs	4.9 µs	+3.4%
⚡	sleep_100ns	55.1 µs	15.7 µs	×3.5
⚡	sleep_1us	58.6 µs	26.8 µs	×2.2