New internationalization plugin review

[fernandolucchesi]

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1. When deleting a document that contains a translation, one must first remove the reference, and then delete the document.
2. Clicking "restore document" right after deleting a translation, doesn't restore the references
3. Translation references can be set manually, should we display this on the menu for specific users?
4. You can't deleted all translations from the "manage translations ui", and then restore it
5. Can we hide the "Manage Translations" UI for editors? This will confuse editors since it requires minimum technical understanding of foreign keys and databases
   
   Also, it is possible (with manage translations) to unset references without deleting the doc and we cannot go back to that document as per our customization. Open translation button is enabled even after reference is unset.  sanity-io/document-internationalization#162
6. Translation Maintenance tab no longer available.