Improve static typing and mypy compatibility

[pabo99]

Description

• Update type annotations across multiple scripts
• Add explicit type casts where needed
• Refactor functions to pass mypy strict mode
• Add mypy.ini basic configuration for Python 3.11

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)
• Documentation update
• Content addition/modification
• Other: Implementing the mypy type checker

Files Modified

• utils/container.py
• utils/download_and_sync_courses.py
• utils/generateresources.py
• utils/runtests.py
• utils/update_assignment_problems.py
• utils/upload.py
• utils/validate_content.py
• utils/Pipfile
• stuff/lint.sh
• mypi.ini

Testing

• I have tested the changes locally
• I have verified that all test cases pass
• I have checked that the content is accurate
• I have reviewed the changes for typos/errors

Checklist

• My code follows the project's style guidelines
• 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
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules