Implement SHADER_PRIMITIVE_INDEX on all Backends

[cwfitzgerald]

Checklist

• Run cargo clippy.
• Run RUSTFLAGS=--cfg=web_sys_unstable_apis cargo clippy --target wasm32-unknown-unknown if applicable.
• Add change to CHANGELOG.md. See simple instructions inside file.

Connections

Closes #3269

Description

Enables SHADER_PRIMITIVE_INDEX where applicable.

Testing

Tested locally using the shader-primitive-index test

[codecov-commenter]

Codecov Report

Merging #3272 (4e5fc52) into master (3d33ace) will increase coverage by 64.97%.
The diff coverage is 83.33%.

@@             Coverage Diff             @@
##           master    #3272       +/-   ##
===========================================
+ Coverage        0   64.97%   +64.97%     
===========================================
  Files           0       82       +82     
  Lines           0    39480    +39480     
===========================================
+ Hits            0    25654    +25654     
- Misses          0    13826    +13826     

Impacted Files	Coverage Δ
wgpu-hal/src/dx11/adapter.rs	0.00% <0.00%> (ø)
wgpu-hal/src/dx12/adapter.rs	81.53% <100.00%> (ø)
wgpu-hal/src/gles/adapter.rs	83.96% <100.00%> (ø)
wgpu-core/src/track/mod.rs	75.18% <0.00%> (ø)
wgpu-core/src/hub.rs	60.67% <0.00%> (ø)
wgpu-hal/src/gles/conv.rs	74.35% <0.00%> (ø)
player/src/lib.rs	53.31% <0.00%> (ø)
wgpu-core/src/device/life.rs	84.22% <0.00%> (ø)
wgpu-hal/src/vulkan/conv.rs	71.76% <0.00%> (ø)
wgpu-hal/src/vulkan/mod.rs	56.37% <0.00%> (ø)
... and 75 more

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[teoxoy]

I checked the specs and this looks good!

Seems we were missing checks in naga for glsl (filed https://github.com/gfx-rs/naga/issues/2163).
We are also missing version checks for msl but we don't have knowledge of the platform in naga (whether it's Metal for MacOS or iOS). filed https://github.com/gfx-rs/naga/issues/2164