Scripts in dev_tools would benefit from updated and additional documentation

[mhucka]

Description of the issue

Most of the scripts in dev_tools/ do are not described anywhere, most don't support a --help or similar command-line argument, and most either lack a usage description in comments within the file, or what is there is out of date. For example, dev_tools/modules.py has a usage docstring at the top of the file (and prints it if you run it with --help), but the code accepts other arguments that are not mentioned.

It would benefit developers to add a README file to dev_tools/ that summarizes the contents of that directory, and also to add usage info (preferrably via a --help argument if possible, or at least comments at the top of the file) to those scripts that are meant to be invoked from the command line.

How to reproduce the issue

Inspecting the dev_tools/ directory and the code therein, the issue becomes evident.

Cirq version

1.5.0.dev