Split tests into multiple files

[jcbhmr]

BLOCKED by #57 DO NOT undraft this until #57 is merged

This PR would...

• [x] Split tests into multiple files
• [x] Match with the same code from #57 which was on the old test suite
• [x] Use plain tsx instead of vitest
• [x] Remove vitest
• [x] Remove ava config from package.json

[jcbhmr]

Closed in favor of doing all the code migration first before splitting tests