Add support for IndexFormat::Uint16 (#2990)

# Objective

while testing wgpu/WebGL on mobile GPU I've noticed bevy always forces vertex index format to 32bit (and ignores mesh settings). 

## Solution

the solution is to pass proper vertex index format in GpuIndexInfo to render_pass

pipelined/bevy_pbr2/src/render/light.rs

@@ -797,7 +797,7 @@ impl Draw<Shadow> for DrawShadowMesh {
             let gpu_mesh = meshes.into_inner().get(mesh_handle).unwrap();
             pass.set_vertex_buffer(0, gpu_mesh.vertex_buffer.slice(..));
             if let Some(index_info) = &gpu_mesh.index_info {
-                pass.set_index_buffer(index_info.buffer.slice(..), 0, IndexFormat::Uint32);
+                pass.set_index_buffer(index_info.buffer.slice(..), 0, index_info.index_format);
                 pass.draw_indexed(0..index_info.count, 0, 0..1);
             } else {
                 panic!("non-indexed drawing not supported yet")

pipelined/bevy_pbr2/src/render/mod.rs

@@ -685,7 +685,7 @@ impl RenderCommand<Transparent3d> for DrawMesh {
         let gpu_mesh = meshes.into_inner().get(mesh_handle).unwrap();
         pass.set_vertex_buffer(0, gpu_mesh.vertex_buffer.slice(..));
         if let Some(index_info) = &gpu_mesh.index_info {
-            pass.set_index_buffer(index_info.buffer.slice(..), 0, IndexFormat::Uint32);
+            pass.set_index_buffer(index_info.buffer.slice(..), 0, index_info.index_format);
             pass.draw_indexed(0..index_info.count, 0, 0..1);
         } else {
             panic!("non-indexed drawing not supported yet")

pipelined/bevy_render2/src/mesh/mesh/mod.rs

@@ -538,6 +538,7 @@ pub struct GpuMesh {
 pub struct GpuIndexInfo {
     pub buffer: Buffer,
     pub count: u32,
+    pub index_format: IndexFormat,
 }
 
 impl RenderAsset for Mesh {
@@ -567,6 +568,7 @@ impl RenderAsset for Mesh {
                 label: None,
             }),
             count: mesh.indices().unwrap().len() as u32,
+            index_format: mesh.indices().unwrap().into(),
         });
 
         Ok(GpuMesh {