Switch to default PartialEq implementation for RenderResourceBinding

[mvlabat]

This should fix #858.

I'm a noob in rendering, but I assumed that changing the dynamic index of a binding should invalidate it. It works (in my example I can see materials changed), though I'm not sure about the performance implications of this. I guess excluding dynamic index from PartialEq implementation was done on purpose. Probably there's a better way to solve the issue.

[cart]

Yeah I'm pretty sure this solves #858, but I'm also worried about performance. We don't want to "rebind" the dynamic uniform buffer when there is a different uniform index / create a new bind group for each buffer/index combo.

[mvlabat]

@cart, yeah, understood. I'm trying to come up with a better fix, but my knowledge is really limiting me here. Could you give me a hint what code should I take a look at?

[cart]

Alrighty I've given this some thought and I think I found the "right" solution. Its basically:

1. Move to the default "derive" impls, just like you already did in this pr (which I just verified does solve Changing a material handle doesn't affect how an entity is rendered #858)
2. Add a new function to BindGroupBuilder called "hash_binding(&mut self, binding: &RenderResourceBinding)" and copy the "old" hash implementation there.

That way the normal impl behaves as expected and we move the "special case" logic to the place that needs it.

[cart]

bevy/crates/bevy_render/src/renderer/render_resource/bind_group.rs

Line 38 in d6eb647

impl BindGroupBuilder {

[cart]

I guess specifically we would replace this line with our new "hash_binding" function:

bevy/crates/bevy_render/src/renderer/render_resource/bind_group.rs

Line 48 in d6eb647

binding.hash(&mut self.hasher);

[mvlabat]

Alright, this should work. I also removed the default Hash implementation for RenderResourceBinding, since it doesn't seem to be used anywhere else.