Course test mode submodule [#3589550]

Problem/Motivation

We need a test mode for courses that will display:
- the current revisions of the course, its lessons and activities
- all activities (ignoring randomization)

, that will not create statuses or answers
, that will allow free navigation regardless of the normal limitations

Remaining tasks

User interface changes

API changes

Data model changes

Issue fork lms-3589550

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3589550-course-test-mode changes, plain diff MR !173
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