Adjust anon submission tooltip layout issue

[jamesrkiger]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Description

Fixes a problem where the long tooltip on the anonymous submission form caused unwanted overflow from the containing element. I created a separate wrapped-tooltip class for this purpose, since the main goal at the moment is to fix this issue rather than changing existing tooltips on the site. I also switched the element's padding to margin in the anonymous submission scss, as this was causing the tooltip's point to be off center.