feat(core): ldml normalization 🙀

- more progress in the normalization pipeline. Trying to keep it from leaking.
- normalize output to NFC.
- normalize json test data to NFC (both context and expected).
- we do NOT try to normalize the 'embedded' strings currently.
- yet more test data fixes (turns out u+00e0 ≠ u+00e8)

For: #9468