Add GitBot Command for creating pull-requests with upstream updates

[raix]

Summary & Motivation

For any downstream project depending on PlatformPlatform getting updates is currently manual. What if there was a command for updating the project and creating a pull-request with updates?

This pull-request adds a new dev tool command "gitbot" - the command can be run manually and potentially in a GitHub action.

The command pp gitbot runs in "dry-run" mode per default allowing inspection of planned tasks, when ready use the "--write" flag and if running in GitHub Actions then skip confirmation using "-y"

Checklist

• [x] I have added a Label to the pull-request
• [x] I have added tests, and done manual regression tests
• [x] I have updated the documentation, if necessary

[tjementum]

Looking awesome. I will look later today.

[raix]

I'm thinking it would be cool with a github action cron job to run the gitbot

Only thing I needed to test is if the current check for existing branch names checks non local branches - if so the script would already exit and wait for the existing branch / pr to be merged.