Move run submodule out into the new devices plugin

[jeremyfowers]

This PR moves the contents of turnkeyml.run into an optional plugin called turnkeyml_plugin_devices. That plugin must be installed to gain access to the benchmark Tool.

Design notes:

• A new test, benchmark.py, is introduced, however it requires that turnkeyml>=4.0.0 be released before it can run. So, we will enable that in a follow-up PR. A lot of the cli.py tests moved in there.
• The example_combined and example_rt example plugins have been removed because, now, they were just essentially examples of how to add content to turnkeyml_plugin_devices. That seemed really unnecessary since turnkeyml_plugin_devices has 3 self-contained examples of how to add content (onnxrt, torchrt, tensorrt).

[danielholanda]

Looks good. Only added a few non-blocking suggestions.