WebGPU: The Async runs seem to only measure the launch of the work, but don't wait until it's finished

[dneto0]

I'm not sure what the intent of the Async variations of benchmarks are.

For example, here's one result on my M1 Pro:

Feature Extraction on webgpu	957.76	142.965
Feature Extraction on webgpu/Benchmark	957.76	142.965
Feature Extraction on webgpu/Benchmark/Sync	957.745	142.955
Feature Extraction on webgpu/Benchmark/Async	0.01499998569	0.009999990463

The async variations seem to only measure the launch of the work, and don't wait for the result to resolve. Is that the intention?

[rmahdav]

Sync and async measurements came from the speedometer framework and the async measurement means nothing meaningful here.
Can we remove it to prevent confusion @camillobruni @danleh?

[rmahdav]

@camillobruni can you please take care of this issue? Thank you!