Fixes #5370
Fixes #5344

* Specify the density and range of `subgroup_id`
* Add `num_subgroups` built-in value

Allow uniform address space to use same layout constraints as other
address spaces

Fixes #5384

Requires that any resources used by any bind groups set during command
encoding must be live/valid/not destroyed. This is a behavior change
from the prior text, which suggested that only resources used by a
"command" (presumably a draw/dispatch) were validated.

The updated validation described in this change matches the WebGPU CTS
and the behavior of multiple implementations.

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Co-authored-by: Andy Leiserson <[email protected]>

Fix #5350

…5421)

Reorder columns to put "sampler filtering" last, and rows to put
"unfilterable_float" last.

Then the validation rules is "it's always ok to move up or left".

Issue: #5355

This PR added immediate validation section to the proposal document.

Fixes:#5318

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Co-authored-by: Copilot <[email protected]>
Co-authored-by: Kai Ninomiya <[email protected]>

Bikeshedding of name. 
We think that 'vec2u' is a better name since wgsl doesnt have 64 bit
types and this feature is functionality built around key value pairs.
The best known use case here is visibility buffers (depth/drawId).

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Co-authored-by: Peter McNeeley <[email protected]>
Co-authored-by: dan sinclair <[email protected]>

Refs #5365

* Adds two new built-in values under the subgroups enable extension
  * subgroup_id - ID of subgroup in the workgroup
  * num_subgroups - number of subgroups in the workgroup

Some were H2, some were H3.