added downlevel restriction error message for InvalidFormatUsages error

[Seamooo]

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
link to issue

Description
As mentioned in the issue, texture format usages that are not possible due to downlevel incompatibility have the same error message as if a usage incompatible with the WebGPU specification is specified. This PR adds a third parameter to the InvalidFormatUsages error, specifying if the error was due to a downlevel incompatibility. Additionally this third parameter is populated by checking against the webgpu allowed usages for the texture format in question.

Testing
This PR was tested by running

device.create_texture(&wgpu::TextureDescriptor {
    label: None,
    size: wgpu::Extent3d {
        width: 1,
        height: 1,
        depth_or_array_layers: 1,
    },
    mip_level_count: 1,
    sample_count: 1,
    dimension: wgpu::TextureDimension::D2,
    format: wgpu::TextureFormat::Rg32Uint,
    usage: wgpu::TextureUsages::STORAGE_BINDING,
});

where device is of type wgpu::Device.
This is within the specification, and within the format features table, however unsupported by the hardware I'm running.
The observed error message is

thread 'tests::test_create_texture' panicked at 'wgpu error: Validation Error

Caused by:
    In Device::create_texture
    Texture usages STORAGE_BINDING are not allowed on a texture of type Rg32Uint due to downlevel restrictions

', wgpu/wgpu/src/backend/direct.rs:2391:5

Additionally to assert that the original error message without downlevel restrictions is behaving correctly the below snippet was run

device.create_texture(&wgpu::TextureDescriptor {
    label: None,
    size: wgpu::Extent3d {
        width: 1,
        height: 1,
        depth_or_array_layers: 1,
    },
    mip_level_count: 1,
    sample_count: 1,
    dimension: wgpu::TextureDimension::D2,
    format: wgpu::TextureFormat::R16Uint,
    usage: wgpu::TextureUsages::STORAGE_BINDING,
});

This is both outside the specification and the table referenced. The error observed in this case is

thread 'tests::test_create_texture' panicked at 'wgpu error: Validation Error

Caused by:
    In Device::create_texture
    Texture usages STORAGE_BINDING are not allowed on a texture of type R16Uint

', wgpu/wgpu/src/backend/direct.rs:2391:5

[cwfitzgerald]

Thanks for this! Please just add to the changelog that the error was improved and we should be g2g

[cwfitzgerald]

Failures on nightly are unrelated.