This is based on PR #19284 and is part of the
series of work related to the proposal #18134.
Adds VideoModule.public_view() to enable
unenrolled and anonymous users to view the video
contents of a public course.
When an unenrolled or anonymous user accesses the
video content of a public course, the
public_view() introduced in the previous PR is
used instead of student_view() method.