Resolve "Distribution of requests per assignment over a lab"

What does this mr do?

Basically creates a bar chart that plots the assignments of a lab against the number of requests for each respective assignment. See #583 (closed) for initial concept diag.

Screenshots

The wireframe places graphs above the table, this will be changed later. For now since there is only one statistic, it is more appropriate that the chart comes below the table.

Does this MR meet the acceptance criteria?

• I have added a changelog entry to reflect the significant changes I made.
• Tests were created to test the feature.
• I have updated the documentation accordingly.
• I adhere to the style guide.

Closes #583 (closed)