Simplify WaitGroup implementation

[Veykril]

No description provided.

[netlify]

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[codspeed-hq]

CodSpeed Performance Report

Merging #958 will degrade performances by 5.28%

_{Comparing Veykril:veykril/push-rqyrkyttxpol (9b4da36) with master (9cfe41c)}

Summary

❌ 1 (👁 1) regression
✅ 12 untouched

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
👁	amortized[Input]	2.1 µs	2.2 µs	-5.28%

[MichaReiser]

Is there any other benefit than code size reduction. It seems codspeed doesn't like it at all.

[Veykril]

No there isn't. I was curious about the perf impact, I agree this isn't great. Checking if we can actually simplify our impl now

[Veykril]

Hm, we could get rid of the additional Arc as well and re-use the Zalsa arc but that makes the code a lot more ugly (thanks to having to deal with drop order), so this is the best I can come up with. Trading an unwrap with unsafe solely due to polonius borrow checking not being a thing yet :(

[MichaReiser]

@ibraheemdev could you take a look at this PR?