replace faern::oneshot with tokio oneshot

[myrrc]

Resolves: #6221

[codspeed-hq]

Merging this PR will degrade performance by 8.53%

⚡ 1 improved benchmark
❌ 3 regressed benchmarks
✅ 1958 untouched benchmarks
⏩ 89 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	cold_misaligned[(64, 256)]	4.4 ms	5.3 ms	-17.43%
❌	Simulation	search_index_in_range_chunked	5.6 ms	6.6 ms	-15.35%
❌	Simulation	search_index_above_max_chunked	4.8 ms	5.4 ms	-11.18%
⚡	Simulation	chunked_varbin_opt_to_varbinview_builder[(10, 100)]	630 µs	558.7 µs	+12.77%

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 myrrc/fix-6221 (1ea75d8) with develop (402a5ac)²}

Footnotes

1. 89 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. ↩

2. No successful run was found on develop (1b34a5e) during the generation of this report, so 402a5ac was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩