This PR removes comments from our record types, makes initial version
optional, and unifies the order of initial / current version.
- Initial versions are zero by default
- If no current version is provided to `defineMigrations`, migrations
should be undefined
- Fixes TypeScript quirks in versioning (e.g. only initial version)
This PR also:
- Makes migrations optional when empty
- Removes reference to empty migrations
### Change Type
- [x] `major` — Breaking Change
### Test Plan
- [x] Unit Tests
- [ ] Webdriver tests
### Release Notes
- [tlschema] Improve `defineMigrations`
- [editor] Simplify migration definitions
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