entrypoint definition and arg parsing

[benedikt-voelkel]

• consolidate entrypoint implementation
• arg parsing structure for user and framework-specific args
• combine/merge/align with current approach used in run.py

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Added later by MC:
Additional steps to be covered towards this implementation, mostly related to the possibility of running different cases (even dummy ones) than the cut optimization for sim.

• Improve flexibility of the tool
  • Accept use-case entrypoints with different signatures (e.g. no need to pass config for example use case)
  • Remove all references to cut optimization in o2tuner core codebase
• Improve use-case parsing managing typical errors in regular way (i.e. not letting Python crash miserably)
  • Use custom logging utility
• Assume path of python helpers to be the base directory of the recipe (this improves portability of recipes and reduce need for fixes from user)