Elementor support for Courses

[brianhogg]

Description

• Adds native Elementor support for courses.
• Adds several basic Elementor widgets, which are added into the editor when first editing a course with Elementor after this update is in place.
• Adds new [lifterlms_course_instructors] shortcode and associated Elementor widget.
• Adds link in the native Elementor menu to Launch Course Builder.

How has this been tested?

Manually

Screenshots

Checklist:

• [x] This PR requires and contains at least one changelog file. <!-- To create a changelog yml file: npm run dev changelog add -- -i and follow the prompt. See also: https://github.com/gocodebox/lifterlms/blob/trunk/packages/dev/README.md#changelog-add -->
• [x] My code has been tested.
• [x] My code passes all existing automated tests.
• [x] My code follows the LifterLMS Coding & Documentation Standards.

[kimcoleman]

Adding notes here that I have locally tested this and the DB upgrade worked fine.