Add DeviceDescriptor.default_queue

[ErichDonGubler]

Description
A clear and concise description of what the bug is.

• The WebGPU spec. specifies that GPUDeviceDescriptor (viz., our DeviceDescriptor type) should contain a field called defaultQueue of type GPUBufferDescriptor, with default value set to {}.
• GPUBufferDescriptor inherits from GPUObjectDescriptorBase, which means that a label can be specified.

☝🏻 We don't implement this yet. It's a relatively recent addition to the spec., so that's not a surprise, but we need it to fully implement the WebGPU spec.

Repro steps
Ideally, a runnable example we can check out.

TODO

Expected vs observed behavior
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TODO

Extra materials
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It looks like the easiest way to implement this is to add the new field as the spec. specifies to DeviceDescriptor, and then use the label here.

Platform
Information about your OS, version of wgpu, your tech stack, etc.

N/A