Fix removeEntity bug

[speigg]

If the same entity is removed twice, the ECS currently enters an invalid state.

ALSO, due to the design entity recycling in bitECS, there is no guarantee that an Entity won't be recycled before it appears in an exit query, meaning any getComponent calls in exit queries are potentially invalid.

This PR fixes these issues, mainly by adding an EntityRemovedComponent (and updating exit queries to respond to this) and deferring actual entity removal until the end of the frame.

Summary

A summary of changes being made in this PR

Checklist

• Pre-push checks pass npm run check
  • Linter passing via npm run lint
  • Unit & Integration tests passing via npm run test:packages
  • Docker build process passing via npm run build-client
• If this PR is still a WIP, convert to a draft
• When this PR is ready, mark it as "Ready for review"
• Changes have been manually QA'd
• Changes reviewed by at least 2 approved reviewers

References

References to pertaining issue(s)

QA Steps

1. git checkout pr_branch_name
2. npm install
3. npm run dev-reinit
4. npm run dev

List any additional steps required to QA the changes of this PR, as well as any supplemental images or videos.

Reviewers

@HexaField @speigg @NateTheGreatt