fix: Destroy and create bodies after step is done

[spydon]

Description

This creates and destroys bodies after stepDt is done to avoid concurrency issues from destroying bodies based on for example taps or other gestures that can happen meanwhile stepDt is running.

Fixes: flame-engine/flame#3712

Checklist

• The title of my PR starts with a Conventional Commit prefix (fix:, feat:, docs: etc).
• I have read the Contributor Guide and followed the process outlined for submitting PRs.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

Related Issues

[drrnbrns]

I just stumbled upon an issue related to this change. In world.dart, the bodies are handled as expected (bodiesToCreate and bodiesToDestroy) but joints are added to jointsToCreate and jointsToDestroy but then never processed. That means nothing actually happens when adding or destroying a joint when the world is locked. Should I log a bug about this? The 4 lists should probably be private too, BTW.

[spydon]

I just stumbled upon an issue related to this change. In world.dart, the bohisdies are handled as expected (bodiesToCreate and bodiesToDestroy) but joints are added to jointsToCreate and jointsToDestroy but then never processed. That means nothing actually happens when adding or destroying a joint when the world is locked. Should I log a bug about this? The 4 lists should probably be private too, BTW.

Thanks for reporting this, can you try this PR if it solves your problem?
#110

[drrnbrns]

Thanks, following up on that PR!