Refactored print_latest_commits.py to return the latest viable commit from master (#79422)
Relates to #76700
**Overview:** Originally `print_latest_commits.py` returned a list of commit SHAs on master from the last M minutes, outputted the individual workflow results, and also displayed if a given commit was promoteable to the viable/strict branch. I realized using this time-based method of retrieving SHAs wasn't the most effective since it takes ~4 hours for all of the HUD tests to run. Since this script will be used to find the latest green commits to promote to viable/strict, I refactored the code to instead collect all of the SHAs that differ between master and viable/strict and output most recent stable commit.
**Example Output:** This script just prints out the latest viable commit on master. If no new commits on master are promote-able, the script outputs the latest commit on viable/strict.
**Test Plan:** While implementing the code, I compared the output of the `get_latest_commits` method with the HUD to make sure it matched. I also ensured that the results from `isGreen` matched those on the HUD and cross checked the final output with the HUD.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/79422
Approved by: https://github.com/janeyx99, https://github.com/seemethere
