[SpeedGrader] Add "Submit on Behalf of Student" Button

[tobe_baeyens]

Problem statement:

The current option to submit a file on behalf of a student is only available through the Gradebook by clicking on the cell that correspondents to the right assignment and the right student, opening the side menu, and selecting "Submit for Student." While this is a useful feature, it is not easily accessible for instructors who primarily use SpeedGrader to manage and evaluate submissions.

Proposed solution:

Add the "Submit on Behalf of Student" button directly to the side panel in SpeedGrader.

User role(s):

instructor