Summary:
- Remove unused Form file (Label.ts)
- Fix Firefox-specific bug in Forms, where mouse selection wasn't working in textarea.
- Focus and set cursor in textarea on click.
- Save on blur but only when focus stays within the Grist app, as for editing cells.
- Make paragraph margins of rendered form match those in the form editor.
Test Plan: Tested manually on Firefox and Chrome; relying on existing tests that nothing broke.
Reviewers: jarek
Reviewed By: jarek
Differential Revision: https://phab.getgrist.com/D4281
063df75204