Migrate Bloom to spec_v2

[ecoskey]

Objective

• migrate bloom to spec_v2

Testing

• bloom_3d example works

For reviewers:

Please bikeshed! This is where we start to make patterns for using spec_v2. Some initial thoughts:

• all the .as_mut().unwrap() obviously won't work. We need accessors of some kind, what should that look like?
• Similarly, base descriptors can't always fill in every field. Should we add a set of placeholder values?
  • @atlv24 and @tychedelia have mentioned removing custom base descriptors, and providing a single default descriptor. I'm not convinced it's a good solution yet, but it's worth considering.
• Getting resources from the specializer outside specialization feels gross. GetBaseDescriptor seems to emphasize this pattern.
  • should we remove GetBaseDescriptor entirely?
  • I think a good pattern might be storing static pipeline resources (shaders, layout) on a plain resource, and using a base_descriptor method on that resource to create the SpecializedCache. That way, specializers would only contain the things they need to perform specialization.

[IceSentry]

We don't need those anymore 👀