After changes from #31472, the user service of a "leaf" XBlock gets overridden
with the one created for its parent (SequenceBlock). Therefore, the
`requires_per_student_anonymous_id` is ignored in these XBlocks. The
subsequent renders of an XBlock (e.g., when requesting the solution) use
the student-specific IDs.
This removes choosing the proper ID (course-specific or student-specific) from
the runtime initialization. Instead, both IDs are passed to the user service.
There are only two XBlocks that relied on the
`requires_per_student_anonymous_id` - `ProblemBlock` and `HtmlBlock`. They
now request the "deprecated" (student-specific) user ID directly from the user
service.
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