Package tmtestnet

Ideally we'd want the `tmtestnet` tool to not be a massive monolithic Python script at some point. The best approach here would be to create a proper Python package for it and submit it to PyPI.

That way developers could simply just:

```bash
pip3 install -U tmtestnet
```

and they'd have access to the functionality from their command line.

The biggest challenges with this are:
1. splitting the code up meaningfully into separate files in a package, and
2. embedding the Terraform and Ansible scripts into the Python package such that the Python script can access those Terraform/Ansible scripts at runtime.

Start by locating the monolithic tmtestnet Python script and the Terraform and Ansible scripts it uses. Define a package structure and runtime asset strategy, then verify that pip3 install -U tmtestnet provides the command-line functionality and can access those scripts after installation.

Written by the indexing model from the issue text.