Use jemalloc in benches with decay disabled

[Veykril]

No description provided.

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[codspeed-hq]

CodSpeed Performance Report

Merging #725 will improve performances by 11.1%

_{Comparing Veykril:veykril/push-plmkuomkutky (b195eb6) with master (38b8976)}

Summary

⚡ 1 improvements
✅ 8 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	mutating[30]	18 µs	16.2 µs	+11.1%

[Veykril]

I guess a faster allocator alone will probably make allocator noise less visible