[MICROBA-1209]
Part of the modulestore cleanup/removal in the certificates app. The function `list_with_level_from_course_overview` was temporary. Cleaning this up. Modifying the original `list_with_level` to accept a course-id/course-key as it doesn't actually need the entire course object.
* Update `list_with_level` function to accept a course run id/course-key
* Remove `list_with_level_from_course_key` function (and update any functions using it to use `list_with_level` again)
[MICROBA-1238]
- Remove unused `course` arguments from certificate generation functions
Part of our cleanup after removing use of the modulestore from the Certificates app.
[MICROBA-1208]
* consolidate `has_html_certificates_enabled` and `has_html_certificates_enabled_from_course_overview`, the latter of the two functions was created for use during our transition away from using the modulestore in the certificate app.
[MICROBA-1178]
- remove modulestore usage in `generation_handler.py`
- add duplicate functions that utilize a CourseKey or CourseOverview to remove dependence on modulestore (this will be cleaned up (if possible) at a later part of this refactor)
- add python API function to `content`/`course_overview` app that will retrieve a single CourseOverview (rather than a serialized list of dicts of CourseOverview data)
[MICROBA-1077]
* Skip bulk certificate invalidation during bulk regeneration. I couldn't come up with a reason to continue to invalidate certificates right before we attempted regeneration.
[MICROBA-1109]
* Remove the requirement for the `auto_certificate_generation` waffle switch to be enabled in order for a learner to be eligible for a certificate. This switch should control _when_ a certificate is generated, not _if_ a certificate will be generated for a learner.
* Move the `auto_certificate_generation_enabled` check to happen before we try to generate v2 certificates in signals.py
* Update unit tests
* Update documentation
