Migrate to Vite

[RichDom2185]

Description

Supersedes #2327. Supersedes #2508.

Closes #2933. Will need to remove CRA compatibility layers after (part of #2990).

TODO:

• [x] Devserver
• [x] Build
• [x] Somehow Admin Panel renders as an iframe that blocks all subsequent interactions (resolved in ce5a1c6517fa7743d9df5d2fb9643b0bb42b1245)
• [ ] GameSimulator crashes with runtime error (fixed by #2997)
• [ ] Test scripts
• [ ] Manually test everything
• [ ] Java-slang not working
• [ ] C-slang not working
• [ ] Service worker

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update
• [x] Code quality improvements

How to test

Checklist

• [x] I have tested this code
• [ ] I have updated the documentation