feat(iddfs): make IDDFS more efficient by using IndexSet internally

[samueltardieu]

This causes an API change as using an IndexSet requires the type to implement Hash.

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #595 will degrade performances by 43.94%

_{Comparing better-iddfs (cd4ddb0) with main (e99545d)}

Summary

⚡ 1 improvements ❌ 2 regressions ✅ 33 untouched benchmarks

:warning: Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	better-iddfs	Change
❌	fill-corner_to_corner_iddfs	4.2 ms	7.4 ms	-43.94%
⚡	fill-no_path_fringe	1.2 ms	1.1 ms	+12.36%
❌	corner_to_corner_iddfs	1.5 ms	2.4 ms	-36.58%

[samueltardieu]

Bad performance report, abandoning