Add data point for packed_4x8_integer_dot_product extension

[chrisdavidmills]

Summary

Chrome 123 supports the readonly_and_readwrite_storage_textures language extension (see WGSLLanguageFeatures), which allows:

• 32-bit integer scalars packing 4-component vectors of 8-bit integers to be used as inputs to dot product instructions
• and packing and unpacking instructions with packed 4-component vectors of 8-bit integers to be used

In your WGSL shader code.

This PR adds a data point for the language extension.

See https://developer.chrome.com/blog/new-in-webgpu-123#dp4a_built-in_functions_support_in_wgsl for the data source.

Test results and supporting details

Related issues

Project issue: mdn/content#36349