chore: add an internal divan fork

[art049]

• chore: initial fork of divan
• chore(divan_fork): integrate the fork within the workspace
• fix(divan_fork): fix existing test suites
• feat(divan_fork): add the codspeed walltime collection point

[codspeed-hq]

CodSpeed Walltime Performance Report

Merging #69 will create unknown performance changes

_{Comparing fork-divan-internally (95b1ea6) with main (fedf402)}

Summary

🆕 2 new benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
🆕	fibo_100	N/A	3.6 µs	N/A
🆕	fibo_500	N/A	7.2 µs	N/A

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #69 will not alter performance

_{Comparing fork-divan-internally (95b1ea6) with main (fedf402)}

Summary

✅ 54 untouched benchmarks

[GuillaumeLagrange]

olgtm, let me know if you need my input once it's a module and not a crate 😎