Split Bundle and StaticBundle

[SkiFire13]

Objective

• Splitted off from Bundle refactor - Option bundles and Box<dyn Bundle> #19491
• Split Bundle into one type representing a static set of component types (StaticBundle) and one that will be used for representing a possibly dynamic set of components.

Solution

• Create a new StaticBundle type, mirroring Bundle for now
• Switch all APIs that need to statically know the components in a Bundle (i.e. from its type) to use StaticBundle
• Add &self parameters to Bundle to ensure all APIs that use it have a concrete instance to work with in the future.

Additional notes

For now this doesn't do anything functionally, as Bundle still requires the components to be statically fixed. However this opens the doors for changes to the Bundle trait that allow dynamic components without impacting APIs that actually rely on static components.

[ElliottjPierce]

Looks good to me. The parallel contents of code for StaticBundle vs Bundle is kinda annoying, but I know that's changing in the next prs, so I'm not worried about it.

[alice-i-cecile]

Some small notes on docs that I think we should clean up quick. I would really appreciate a paragraph or two of module docs laying out these traits and how they interconnect, but that's fine to leave to follow-up if you prefer.

More importantly, I'm not sure why we should keep a split between DynamicBundle and Bundle around after these changes. It looks like Bundle should now be object-safe, allowing us to merge them together.

I haven't done a deep dive on this area of the code in a while though, so please feel free to explain why we can't / shouldn't do that :)

[SkiFire13]

More importantly, I'm not sure why we should keep a split between DynamicBundle and Bundle around after these changes. It looks like Bundle should now be object-safe, allowing us to merge them together.

Bundle is not object safe yet (it still has a bunch of generic functions without where Self: Sized) but this will change in a followup PR.

However even then it will be a bit of a hassle to remove DynamicBundle. In the unsplitted PR I limited myself to renaming it to ComponentsFromBundle to avoid confusion with dynamic bundles after trying to remove it. The issue is that the insert_by_ids method internally uses it with a struct wrapping some OwningPtrs, which is not Send + Sync + 'static, while Bundle requires them (but not DynamicBundle/ComponentsFromList!). Removing those requirements is possible but leads to ton of boilerplate elsewhere (e.g. all commands require them).