shell: Polish repl code

This clean up and move stuffs in order to simplify or to make stuff explicit.

• Fix typing
  • No more mypy type error for bliss.shell.cli
  • Create a BlissAppSession to store more than what prompt toolkit stores
    • This could be reworked in the future
• Remove monkey patches
  • The completer is now setup inside BlissRepl
  • The statusbars are still using monkey patching but setup at run time by BlissRepl
• Reorganize some code from bliss.shell.cli
  • Split a bit more what is about app and lib
  • ... by creating a single class or function into a single module
  • Split repl.py into bliss_repl.py, bliss_app_session.py, bliss_output.py
  • Move session_files_templates.py into bliss.shell.main
  • Create config.py to remove anything from __init__
    • This module will probably grow up in the future to feature persistence
• Make sure the app session is properly propagated
  • Drop output from the greenlet context and only use app_session
• The remaining code from bliss.shell.cli.repl.py is about the setup and bootstrap of BlissRepl
  • This could be reworked in the future to split a bit more what is about app and lib