update for wgpu 0.8 (#1959)

Changes to get Bevy to compile with wgpu master.

With this, on a Mac:
* 2d examples look fine
* ~~3d examples crash with an error specific to metal about a compilation error~~
* 3d examples work fine after enabling feature `wgpu/cross`


Feature `wgpu/cross` seems to be needed only on some platforms, not sure how to know which. It was introduced in gfx-rs/wgpu-rs#826

src/loader.rs

@@ -116,35 +116,35 @@ async fn load_gltf<'a, 'b>(
 
  if let Some(vertex_attribute) = reader
  .read_positions()
- .map(|v| VertexAttributeValues::Float3(v.collect()))
+ .map(|v| VertexAttributeValues::Float32x3(v.collect()))
  {
  mesh.set_attribute(Mesh::ATTRIBUTE_POSITION, vertex_attribute);
  }
 
  if let Some(vertex_attribute) = reader
  .read_normals()
- .map(|v| VertexAttributeValues::Float3(v.collect()))
+ .map(|v| VertexAttributeValues::Float32x3(v.collect()))
  {
  mesh.set_attribute(Mesh::ATTRIBUTE_NORMAL, vertex_attribute);
  }
 
  if let Some(vertex_attribute) = reader
  .read_tangents()
- .map(|v| VertexAttributeValues::Float4(v.collect()))
+ .map(|v| VertexAttributeValues::Float32x4(v.collect()))
  {
  mesh.set_attribute(Mesh::ATTRIBUTE_TANGENT, vertex_attribute);
  }
 
  if let Some(vertex_attribute) = reader
  .read_tex_coords(0)
- .map(|v| VertexAttributeValues::Float2(v.into_f32().collect()))
+ .map(|v| VertexAttributeValues::Float32x2(v.into_f32().collect()))
  {
  mesh.set_attribute(Mesh::ATTRIBUTE_UV_0, vertex_attribute);
  }
 
  if let Some(vertex_attribute) = reader
  .read_colors(0)
- .map(|v| VertexAttributeValues::Float4(v.into_rgba_f32().collect()))
+ .map(|v| VertexAttributeValues::Float32x4(v.into_rgba_f32().collect()))
  {
  mesh.set_attribute(Mesh::ATTRIBUTE_COLOR, vertex_attribute);
  }