This PR cleans up the file names and imports for @tldraw/tlschema.
It also:
- renames some erroneously named validators / migrators (e.g.
`pageTypeValidator` -> `pageValidator`)
- removes the duplicated `languages.ts` and makes `tlschema` the source
of truth for languages
- renames ID to RecordId
### Change Type
- [x] `major` — Breaking Change
### Release Notes
- [editor] Remove `app.createShapeId`
- [tlschema] Cleans up exports
