on_submitted_work_done / onSubmittedWorkDone is unimplemented on WebGPU

[ArthurBrussee]

on_submitted_work_done works for native platforms but is unimplemented!() for WebGPU.

See also https://github.com/gfx-rs/wgpu/discussions/5122, https://github.com/gfx-rs/wgpu/pull/5012

[ErichDonGubler]

The Web platform has GPUQueue.onSubmittedWorkDone, but our callback-based approach in WGPU either needs to be adapted to the web, or we need to rethink the API for WGPU to be resolve-able a la Promises (maybe via await?).

[cwfitzgerald]

We already have adapters for mapAsync, so this should be fine to implement

[ArthurBrussee]

Seems this was merged! Thanks all, looking forward to wgpu 26.