Use exe instead of python VE

## Problem
distributing the environment as a python VE is highly variable and subject to periodically going spastic.

## Solution
Distribute the mbed-cli environment as a .exe, use a tool like Py2Exe or similar to take the minimal scrips and wrap them up into a .exe and distribute that instead to allow for tighter version control.

The issue names the mbed-cli environment and Py2Exe but no repository files or tests. Start by inspecting how the current Python virtual environment is packaged in this installer; done means a reproducible .exe distribution with controlled dependencies replaces that environment.

Written by the indexing model from the issue text.