Specify when missing texture format is a downlevel restriction

[kpreid]

Is your feature request related to a problem? Please describe. wgpu started supporting software rendering and as a result I got this error from my tests running on headless CI with the llvmpipe software renderer:

wgpu error: Validation Error
Caused by:
    In Device::create_texture
      note: label = `EverythingRenderer::linear_scene_texture`
    Texture usages RENDER_ATTACHMENT are not allowed on a texture of type Rgba16Float

This is a downlevel restriction (not-WEBGPU_TEXTURE_FORMAT_SUPPORT) but the error message doesn't say it is, unlike others.

Describe the solution you'd like

Make this error message specify that this is a downlevel issue. This should be possible by, at CreateTextureError::InvalidFormatUsages error printing time, checking the combination requested against the WebGPU specification's required support.