Implement hands on hp-populate-remote

[oadultradeepfield]

Update: I realised that the commits in this PR were created from the wrong branch. I will close this PR and open a new one (#78) from the correct branch. Apologies for the confusion.

Exercise Review

Exercise Discussion

Below is a more detailed description of the changes along with implementation notes:

1. Added an add_origin function in exercise_utils/git.py. This might be helpful in the future. I noticed that there is already a remove_remote implementation, and add_origin is intended to be used in a similar way.
2. To help ensure that the remote repository gitmastery-things is created successfully across multiple attempts, I added a check to delete any existing remote repository with the same name. Please note that this requires setting up delete access for the GitHub CLI via gh auth refresh -h github.com -s delete_repo. I also realised that the GitHub CLI needs to be configured beforehand for this part of the hands-on to work.

Note: The download script tested via test-download.sh works fine. Here is the remote repo I managed to create.

Checklist

• If you require a new remote repository on the Git-Mastery organization, have you created a request for it?
• Have you written unit tests using repo-smith to validate the exercise grading scheme?
• Have you tested the download script using test-download.sh?
• Have you verified that this exercise does not already exist or is not currently in review?
• Did you introduce a new grading mechanism that should belong to git-autograder?
• Did you introduce a new dependency that should belong to app?