chore: return CUDA events from kernel launch

[0ax1]

This PR changes the launch kernel API in vortex-cuda to propagate the pair of CUDA events returned from cudarc::LaunchArgs:launch.

When launching a kernel, CUDAs events are automatically submitted before and after.
The events can be used to wait for a particular kernel to finish or to benchmark a CUDA kernel.

[codspeed-hq]

Merging this PR will not alter performance

✅ 1254 untouched benchmarks
⏩ 1254 skipped benchmarks¹

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_{Comparing ad/proper-return-type (1048b2e) with develop (86b3d02)}

Footnotes

1. 1254 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. ↩

[codecov]

Codecov Report

❌ Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.87%. Comparing base (4bbafe7) to head (1048b2e).
⚠️ Report is 7 commits behind head on develop.

Files with missing lines	Patch %	Lines
vortex-cuda/src/executor.rs	0.00%	12 Missing ⚠️
vortex-cuda/src/for_.rs	0.00%	4 Missing ⚠️

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