Improve QOL for Package Development and Testing

[JPRuskin]

The workflow for users building and testing packages could be improved, e.g. with an argument completer for the update and test scripts to allow folk to tab-complete package IDs.

We could, at the same time, improve the readability and maintainability of the scripts by adding some light comment help and possibly doing a quick formatting pass, and switching from aliases to full names where possible.

e.g. chocolatey-community/chocolatey-packages#2498