Rename "point light" to "clusterable object" in cluster contexts.

[pcwalton]

We want to use the clustering infrastructure for light probes and decals as well, not just point lights. This patch builds on top of #13640 and performs the rename.

To make this series easier to review, this patch makes no code changes. Only identifiers and comments are modified.

Migration Guide

• In the PBR shaders, point_lights is now known as clusterable_objects, PointLight is now known as ClusterableObject, and cluster_light_index_lists is now known as clusterable_object_index_lists.

[BD103]

I added the contentious label because it's a non-trivial breaking change that may affect the ecosystem as a whole. If the rendering people generally agree with this change, it can be switch to X-Blessed.

[alice-i-cecile]

Diff looks fine to me: this really is just a rename. I like the move from light -> "anything that could be clustered". I'd be fine with dropping _object from clusterable_object, but e.g. y_object really needs a noun to go with it and should stay in its current form.

[IceSentry]

I haven't discussed it with other SMEs yet, but I don't think this is contentious. It's pretty much agreed that this code needs a refactor and the change is motivated by future features that we also want.

@BD103 I'm also not sure why you consider it non-trivial, it's just a rename with no behaviour change and the things that are renamed are probably not used by the vast majority of users except advanced users making custom lighting systems. A migration guide entry mentioning the rename seems more than enough to me.

[IceSentry]

I tested a bunch of examples just to make sure nothing was missed and didn't find any regressions.

A note about rust side renames in the migration guide section would be nice. Doesn't necessarily have to be the entire list but at least mention it's not just shader stuff that's been renamed.

LGTM assuming CI is fixed (I think it's just fmt stuff)

[alice-i-cecile]

Once CI is passing I'll merge this in.

[BD103]

@BD103 I'm also not sure why you consider it non-trivial, it's just a rename with no behaviour change and the things that are renamed are probably not used by the vast majority of users except advanced users making custom lighting systems. A migration guide entry mentioning the rename seems more than enough to me.

I mainly marked it as straightforward due to the amount of files being modified, even if those modifications are trivial. It's really up to interpretation, so I'll switch it over. :)

[IceSentry]

@BD103 Ah, I didn't realize that's what you meant by non-trivial, I wasn't thinking about labels, I think the "may affect the ecosystem" part was what confused me. I agree that the straightforward label is fine here.

[BD103]

@BD103 Ah, I didn't realize that's what you meant by non-trivial, I wasn't thinking about labels, I think the "may affect the ecosystem" part was what confused me. I agree that the straightforward label is fine here.

Yup! It was probably confusing because my understanding of Bevy's rendering setup is severely lacking. You didn't understand it because I probably didn't understand it either; I just guessed that a rename may affect existing libraries / plugins.

Either way, glad we got this resolved!