Clarify where GPU related states are stored for WebGPU interop (MLContext, MLCommandEncoder and MLGraph)

[huningxin]

Split from #341, where @wacky6 mentioned

From the current spec, it's unclear where GPU related states are stored (are they on MLCommandEncoder, or MLGraph itself).

I'd agree the spec should improve in this area.

AFAIK, for GPU context, MLContext should maintain a reference to GPU device, MLGraphBuilder created from GPU MLContext should also refer to GPU device to create and compile GPU operators, MLGraph should maintain the compiled GPU operators and persistent/constant GPU resources, MLCommandEncoder should create the command list from GPU device and record operators initialization and compute commands.

@wchao1115 should know more details than me, please feel free to chime in.

[bbernhar]

@huningxin is the group still pursuing this approach? If not, can we close in favor of #688?

[huningxin]

Yes, this one is obsoleted by #688. Closing it.