feat: store Numbas config in backend

[satikaj]

Description

The backend schema and files for task definition were updated to store Numbas config options.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

This was tested with the frontend task editor UI. Upon uploading and configuring Numbas tests, the state is saved even after refreshing the page.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation if appropriate
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have created or extended unit tests to address my new additions
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[ublefo]

db:populate should all be fixed now, added missing columns to the test csv file so task import from csv will work properly. Other csv files will likely also require adjustments since they are used for unit tests.

[ublefo]

Should we change this time delay to an integer (in minutes) as well?

[satikaj]

Daniel plans to have an incremental delay feature which the tutor can enable. So first 2 attempts would have no delay, the next would have a 30 min delay, then 2 hours, and so on until the student has to see the tutor. I've modified the code to accomodate this already.