bevy_ecs: add untyped methods for inserting components and bundles

[Suficio]

This MR is a rebased and alternative proposal to #5602

Objective

• [Merged by Bors] - untyped APIs for components and resources #4447 implemented untyped (using component ids instead of generics and TypeId) APIs for inserting/accessing resources and accessing components, but left inserting components for another PR (this one)

Solution

• add EntityMut::insert_by_id

• split Bundle into DynamicBundle with get_components and Bundle: DynamicBundle. This allows the BundleInserter machinery to be reused for bundles that can only be written, not read, and have no statically available ComponentIds

• Compared to the original MR this approach exposes unsafe endpoints and requires the user to manage instantiated BundleIds. This is quite easy for the end user to do and does not incur the performance penalty of checking whether component input is correctly provided for the BundleId.

• This MR does ensure that constructing BundleId itself is safe

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Changelog

• add methods for inserting bundles and components to: world.entity_mut(entity).insert_by_id

[alice-i-cecile]

I like it! Needs more docs though.

[alice-i-cecile]

Very nice, I'm happy with this now. Please feel free to resolve my previous comments to make reviewing easier.

[alice-i-cecile]

Very nice, I'm happy with this now. Please feel free to resolve my previous comments to make reviewing easier.

[alice-i-cecile]

Controversial because we need to decide between this and #5602.

[jakobhellermann]

I left some comments.

What I would really like to see is a method for inserting a single component that doesn't require manual caching and unsafety (other than OwningPtr).

[Suficio]

Thanks for the review @jakobhellermann @james7132!

I made the following changes to address your review comments:

• init_dynamic_info now caches dynamic bundles and only verifies component existence when creating new bundles.
• init_dynamic_info caches into two hash maps, one for dynamic length bundles and the single component bundle case (additionally caching the storage type).
• Added insert_by_id which only takes ComponentId, turned out very nicely
• insert_bundle_by_id now doesn't require the storage type
• Added insert_bundle_by_id_unchecked which is used by insert_by_id and insert_bundle_by_id but is also available to be used publicly (as it skips an allocation).

[alice-i-cecile]

I like the new changes a lot; this is a much friendlier API now.

[Suficio]

Now that I think about it init_dynamic_info is quite cheap to call so I could get away with creating API that doesn't expose BundleId.

[Suficio]

Worked like a charm, only insert_by_id and insert_bundle_by_id are retained as public APIs.

The only drawback is I had to cache the storage types of bundle components, this seems relatively innocuous but can be relatively easily removed.

[james7132]

This is going to be significantly slower than the typed API, but I don't think there's a solid way around that.

IMO we should clean up the HashMaps used in Bundles, but that's strictly non-blocking and can be tackled in a follow-up PR.

[james7132]

Non-blocking: I feel like this could be better represented by putting StorageType back into BundleInfo and replacing the Vec<ComponentId> with Vec<BundleComponent> which contains both the ID and the storage type. The same for the below.

[Suficio]

Can definitely do this in a follow-up for removing dynamic components!

[Suficio]

Rebased PR

Renamed insert_bundle_by_id to insert_by_ids

[cart]

Looks good to me. I think this is how we should do it. Minimally invasive, which I like.