Fix EntityCloner replacing required components.

[eugineerd]

Objective

Fix #19324

Solution

EntityCloner replaces required components when filtering. This is unexpected when comparing with the way the rest of bevy handles required components. This PR separates required components from explicit components when filtering in EntityClonerBuilder.

Testing

Added a regression test for this case.

[urben1680]

Looks good. Nice that this does not come with an API change.

[urben1680]

I wonder if this can be extended a bit. If you could manually populate the new filter_required field, you could basically make the cloner fit for insert-if-new capability. I certainly would make use of that for my crate.

An API do allow/deny by BundleId would be interesting for me too. 🤔 When this is merged I could implement the features in my own PR and see if this fits into 0.16.1 or not.

[eugineerd]

I wonder if this can be extended a bit. If you could manually populate the new filter_required field, you could basically make the cloner fit for insert-if-new capability. I certainly would make use of that for my crate.

Yeah, that could be useful. Although I don't think new API is supposed to be introduced in patch releases, so I think it's better to leave this PR just as a bugfix for 0.16.1 and add new stuff in 0.17.