fix: staff debug actions depended on legacy courseware URL (#26658)

The Staff Debug Actions didn't work in the Learning MFE
because the underlying JS depended on the URL being
formatted as /courses/<course_key>/... in order to
parse out the course key. This worked in the legacy
experience, but breaks in the chromeless xblock view,
which is rendered under the URL /xblock/<usage_key>/...

The fix is to explicitly pass the course key into the
templated courseware HTML as a data attribute.

TNL-7955