Remove deprecated SetIndexBuffer (without format).

This also simplifies a bunch of code in backends that was used to handle
getting the indexFormat from the pipeline "late".

Bug: dawn:502

Change-Id: Ibae50c8df21323fd391515f6036552e9fb868d93
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/32023
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Stephen White <senorblanco@chromium.org>
diff --git a/examples/CppHelloTriangle.cpp b/examples/CppHelloTriangle.cpp
index 1a879e9..52ec2f9 100644
--- a/examples/CppHelloTriangle.cpp
+++ b/examples/CppHelloTriangle.cpp
@@ -163,7 +163,7 @@
         pass.SetPipeline(pipeline);
         pass.SetBindGroup(0, bindGroup);
         pass.SetVertexBuffer(0, vertexBuffer);
-        pass.SetIndexBufferWithFormat(indexBuffer, wgpu::IndexFormat::Uint32);
+        pass.SetIndexBuffer(indexBuffer, wgpu::IndexFormat::Uint32);
         pass.DrawIndexed(3);
         pass.EndPass();
     }