Timestamp Query Inside Passes (experimental!)

Adds support for the writeTimestamp call inside render and compute passes. This method might not always make a lot of sense on tiler GPUs (so basically any modern GPU) where the ordering of operations inside render passes is not strictly like the order of commands recorded (each tile being executed independently),

Adds the following methods:

voi wgpu::ComputePassEncoder::writeTimestamp(wgpu::QuerySet querySet, uint32_t queryIndex);
voi wgpu::RenderPassEncoder::writeTimestamp(wgpu::QuerySet querySet, uint32_t queryIndex);

The validation is the following:

• querySet must be a valid query set.
• querySet must have been created with wgpu::QueryType::Timestamp.
• queryIndex must be less than querySet's size.
• During the wgpu::Queue::Submit for these commands, querySet must not be destroyed.

The initial tracking bug was https://crbug.com/dawn/434.