Major cleanup

[jeremyfowers]

Closes #196 #193 #183 #182

Summary

• Complete rework of how cached builds are accessed
  • All cache loads are explicitly accessed by the new load-build Tool and turnkeyml.state.load_state() API
    • The load-build tool takes a BUILD_NAME_state.yaml file as input, loads the state of that build, a passes it to the next Tool in the sequence.
    • Provides a --skip-policy argument to make it easy to manage evaluation of large amounts of builds, similar to the skip policy in the old turnkey cache benchmark.
  • The ignition module has been removed
  • The --rebuild CLI argument has been removed
  • The turnkey cache benchmark Tool has been removed
    • Benchmark a pre-built model with turnkey -i path/to/state.yaml load-build benchmark
• The build_model() API has been removed
  • Similar functionality is still available by calling Tool classes directly; Create examples for the new way of using the API #198 will add examples of this
  • All tests and examples for build_model() have been removed
• The benchmark_files() API has been renamed to evaluate_files()
  • Function body has been simplified a lot
  • Only Sequence and Tools should write to stats. All code in the evaluate_files() body has been moved under Sequence.launch().
  • Sequence.launch() does everything needed to manage the sequence, such as launching the monitor. This used to be the responsibility of evaluate_files().
• A new class, FirstTool, has been added to provide convenience and guardrails for Tools that are meant to start a sequence, such as load-build, load-onnx, and discover.
• Special behavior for the exp.SkipBuild exception: any changes to stats are rewound to before that build was loaded, such that skipping a build does not perturb the stats in any way.

[danielholanda]

Looks good and works well

[ramkrishna2910]

Looks really good! I was able test locally on my system.
Added a minor comment.