Summary:
- New styling for forms.
- New field options for various field types (spinner, checkbox, radio buttons, alignment, sort).
- Improved alignment of form fields in columns.
- Support for additional select input keyboard shortcuts (Enter and Backspace).
- Prevent submitting form on Enter if an input has focus.
- Fix for changing form field type causing the field to disappear.
Test Plan: Browser tests.
Reviewers: jarek
Reviewed By: jarek
Differential Revision: https://phab.getgrist.com/D4223
