Deprecate field_by_id special baserow formula function to greatly simplify...

I'd like to merge this into develop, its been well tested and I think it will be much easier to merge it ASAP than leave it hanging until the entire lookup field is ready.

Closes #638 (closed)

Testing Notes

1. Can rename fields still in realtime and formulas are updated
2. Can delete/restore/create fields and formulas with break/be fixed corrospondingly
3. Can export and import a template with a formula still
4. The formula API now returns formulas without field_by_ids
5. Can make formulas, change their types, click the refresh options and get updated options still
6. Can rollback the migration and existing + new formulas still work

Merge Request Checklist

• changelog.md has been updated if required
• Documentation has been updated
• Quality Standards are met
• The UI/UX has been updated following UI Style Guide
• The redoc API pages have been updated for any REST API changes
• The per database user API docs page has been updated for any REST API changes made to endpoints which can be accessed via a user created token
• Has performance been considered and tested when appropriate? Ideally Baserow should be performant when working with hundreds of thousands of rows
• New/Changed Premium features are separated correctly in the premium folder
• There are tests for and it has been checked that any changed/new django ORM code is sensible, doesn't perform N queries and that table models are not generated needlessly or generated with all columns when only a few are needed.