feat: add materials for at-risk learner group (FC-0051)

[SoryRawyer]

This change introduces many new charts and datasets to provide insight into the at-risk learner group. These dashboard additions are meant to copy the structure of the existing course dashboard, but with the at-risk learner group dataset joined to the existing data to filter out any learners that should not be part of the visualizations.

Notes for draft PR review: I'd particularly appreciate feedback on the feasibility of managing duplicate datasets like the approach taken here. There are still one or two more charts to add (specifically around grade distribution in the "Performance" tab).

Specific "at-risk" versions of the following charts and datasets have been added:

• video plays
• watched video segments
• full and partial views of videos
• enrollments
• problem interactions and engagement

Below are screenshots of the dashboard:

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