[wip]: Fixpoint simplifier

[ak3n]

wip

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Pre-submit checklist:

• Branch
  • [ ] Tests are provided (if possible)
  • [ ] Commit sequence broadly makes sense
  • [ ] Key commits have useful messages
  • [ ] Relevant tickets are mentioned in commit messages
  • [ ] Formatting, materialized Nix files, PNG optimization, etc. are updated
• PR
  • [ ] Self-reviewed the diff
  • [ ] Useful pull request description
  • [ ] Reviewer requested