As a result of MDL-41556 (146893d6), the repository/lib.php was included
in submission.php so that its constant FILE_INTERNAL could be used in
field options. Recent development in MDL-50794 (996f7e8) moved the
options declaration to standalone methods but we forgot to check they
work in exsubmission.php too.
This patch moves the repository/lib.php inclusion to where the
library is actually needed.
Additionally it unifies how options are set for overall feedback content
and overall feedback attachment fields.
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