Add a wizard script for local development in `hermetic_build/`

[diegomarquezp]

Setting up my local for development of https://github.com/googleapis/sdk-platform-java/pull/3723 involved quite the amount of trial and error for renaming files, using right locations, etc. Despite I was one of the developers of these scripts and the development guide covers all what's needed, the fact that setting up my local after a few months was toilsome made me think we could use a wizard script.

Such wizard script could simply setup the ${HOME}/.library_generation folder with the necessary tools, maybe asking to input versions or default to what's inferred from pom files (e.g. please introduce generator version (default: x.x.x):). Also installing the scripts dependencies and the python package itself in --editable mode.