Replace orx-concurrent-vec with boxcar

[MichaReiser]

This PR replaces orx-concurrent-vec with boxcar because:

• boxcar is a much smaller dependency 11.1KB without dependencies vs 90.9KB with a handful of dependencies
• orx-concurrent-vec fails to build on 32bit platforms (may be fixed soon)
• boxcar shows better performance

[netlify]

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[codspeed-hq]

CodSpeed Performance Report

Merging #554 will not alter performance

_{Comparing MichaReiser:use-boxcar (7827ca0) with master (7bdf51c)}

Summary

✅ 1 untouched benchmarks

[MichaReiser]

This gives us a 9% perf improvement. I don't think it's very representative for real world applications, unless the application uses multiple databases

@nikomatsakis we may want to reduce the codspeed threshold to a few percent (2-3?) and change the settings to only comment on improvements/regressions. You can do this on the settings page

[MichaReiser]

I close this in favor of #555 which shows even better performance