While looking at the pipeline statistics queries and how it would change webgpu.h, I had the following two questions:

• Should they be allowed in GPURenderBundle? They currently are, but it seems to conflict with our earlier decision to disallow occlusion queries on render bundles.
• Are pipeline statistics queries allowed to be nested, or even interleaved? If not, then endPipelineStatisticsQuery should not take any argument.

+CC @haoxli