vortex-file: Spawn tasks via runtime instead of directly via tokio

[brancz]

Rationale for this change

I upgraded to 0.78 and some automation we have that detects when dependencies use raw tokio::spawn got triggered. We need to control all spawn points, both for correctness testing and for instrumentation purposes. I realize that these spawns are in test code, but I thought since vortex already has the runtime abstractions, it wouldn't hurt to use them in the tests as well (admittedly our tooling is not crazily sophisticated so it can't distinguish whether it's testing code or not).

What changes are included in this PR?

Use TokioRuntime instead of raw tokio::spawn in tests.

What APIs are changed? Are there any user-facing changes?

n/a

[gatesn]

This is great, would love to know what checks you're using so we can run them ourselves!

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 3 improved benchmarks
❌ 2 regressed benchmarks
✅ 1625 untouched benchmarks
⏩ 42 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	rebuild_naive	91.4 µs	109 µs	-16.17%
❌	Simulation	chunked_varbinview_opt_canonical_into[(100, 100)]	305.4 µs	340.4 µs	-10.27%
⚡	Simulation	chunked_varbinview_into_canonical[(1000, 10)]	205.6 µs	169.5 µs	+21.32%
⚡	Simulation	bitwise_not_vortex_buffer_mut[128]	244.4 ns	215.3 ns	+13.55%
⚡	Simulation	bitwise_not_vortex_buffer_mut[1024]	304.7 ns	275.6 ns	+10.58%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing polarsignals:worktree-spawn-rm (4b260ab) with develop (a649d75)}

Footnotes

1. 42 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩