[ros2pkg] Integrate features of 3rd-party ros2-pkg-create CLI tool

[lreiher]

We have recently open-sourced our own package generation tool ros2-pkg-create. Please also see my introductory post on ROS Discourse.

I'm opening this draft PR in response to @tfoote suggesting to integrate ros2-pkg-creates features into the official CLI.

[!NOTE] This PR is not carrying any changes just yet. I'm mainly opening this to share some insights into the features of ros2-pkg-create, how it's different than this repository's ros2 pkg create, and how an integration here could look like. Ideally, we could gather some feedback and suggestions before starting the actual integration efforts.

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Features of ros2-pkg-create

• templates for three types of packages
  • C++ Package
  • Python Package
  • Interfaces Package (msg, srv, action)
• support for basic and advanced features for both C++ and Python
  • publisher
  • subscriber
  • parameter loading
  • launch file (py/xml/yml)
  • service server
  • action server
  • timer callback
  • C++ component
  • C++ lifecycle
  • docker-ros
• interactive CLI questionnaire for options not specified as CLI arguments

Technical Details of ros2-pkg-create

• CLI implemented in Python
• interactive questionnaire based on copier
• templates based on jinja templating engine, see example header
• installable via pip

Differences between ros2-pkg-create and ros2 pkg create

• ros2 pkg create uses empy instead of jinja, see example header
• ros2 pkg create-only features:
  • setting dependencies via CLI arg
  • choosing C++ node vs library
  • choosing cmake vs ament_cmake build types
• ros2-pkg-create-only features:
  • interactive questionnaire for options not via CLI arg; can also use defaults, though
  • generation of more than a barebones C++/Python node, see list of features above (e.g., publisher, launch file, action server, etc.)
  • generation of an interfaces package