Package developer mode

Currently if you want to work on a package you must either directly edit the package and run it from the internal workspace or download it and use --override-input when calling the enclosing workspace. Instead of this, we should allow for package developer mode, i.e. a JSON that keeps trace of which packages are being actively worked on an redirect source requests to that path without the need of --override-input.

This will likely come in the form of a cli tool that provides the ability to quickly swap the mode of a package. Additionally, it would also be good if the workspace contained git hooks disallowing commits until all packages are locked back to prod mode.

• Question: should this be a ros2 cli extension?
• Some potential inspiration: https://github.com/mightyiam/input-branches