Fix CAS shader with explicit FullscreenVertexOutput import

[cart]

Objective

Followup bugfix for #5703. Without this we get the following error when CAS (Contrast Adaptive Sharpening) is enabled:

2023-06-29T01:31:23.829331Z ERROR bevy_render::render_resource::pipeline_cache: failed to process shader:
error: unknown type: 'FullscreenVertexOutput'
   ┌─ crates/bevy_core_pipeline/src/contrast_adaptive_sharpening/robust_contrast_adaptive_sharpening.wgsl:63:17
   │
63 │ fn fragment(in: FullscreenVertexOutput) -> @location(0) vec4<f32> {
   │                 ^^^^^^^^^^^^^^^^^^^^^^ unknown type
   │
   = unknown type: 'FullscreenVertexOutput'

@robtfm I wouldn't expect this to fail. I was under the impression the #import bevy_core_pipeline::fullscreen_vertex_shader would pull "everything" from that file into this one?

[robtfm]

Items need to be either individually imported, or qualified at point of use. I didn’t do glob imports yet.

[Elabajaba]

I ran into the same crash, and this fixed it.

[cart]

Items need to be either individually imported, or qualified at point of use. I didn’t do glob imports yet.

Ah gotcha gotcha. Then this makes perfect sense!