Unified code generation CLI

[hidmic]

Feature request

Feature description

Connected to #560. Description and rationale to be found at ros2/design#310.

Implementation considerations

• Attempt to install Python entry points from ament_cmake packages (Make ament_python_install_package() install a flat Python egg ament/ament_cmake#316).
• Add rosidl_cli package, with a basic rosidl generate CLI. (Add rosidl generate CLI. #567)
• Edit: Add rosidl translate CLI verb for interface definition conversion. (Add rosidl translate CLI. #575)
• Edit: Expose CLI as API. (Expose an API for each rosidl CLI command.  #577)
  • Useful to e.g. perform implicit interface translation on generation.
• Edit: Provide rosidl translate plugins from existing adapter/generator packages:
  • rosidl_adapter (Expose .msg/.srv/.action to .idl conversion via rosidl translate CLI #576)
  • rosidl_generator_dds_idl (Expose .idl to DDS .idl conversion via rosidl translate CLI rosidl_dds#55)
• Provide rosidl generate plugins from existing generator packages:
  • rosidl_generator_c (Expose C code generation via rosidl generate CLI #569)
  • rosidl_generator_cpp (Expose C++ code generation via rosidl generate CLI #570)
  • rosidl_generator_py (Expose Python code generation via rosidl generate CLI rosidl_python#123)
  • rosidl_typesupport_introspection_c (Expose C introspection typesupport generation via rosidl generate CLI #572)
  • rosidl_typesupport_introspection_cpp (Expose C++ introspection typesupport generation via rosidl generate CLI  #573)
  • rosidl_typesupport_c (Expose C typesupport generation via rosidl generate CLI rosidl_typesupport#105)
  • rosidl_typesupport_cpp (Expose C++ typesupport generation via rosidl generate CLI rosidl_typesupport#104)
  • rosidl_typesupport_fastrtps_c (Expose FastRTPS C typesupport generation via rosidl generate CLI rosidl_typesupport_fastrtps#65)
  • rosidl_typesupport_fastrtps_cpp (Expose FastRTPS C++ typesupport generation via rosidl generate CLI rosidl_typesupport_fastrtps#66)
  • rosidl_typesupport_connext_c (Expose Connext C typesupport generation via rosidl generate CLI rosidl_typesupport_connext#67)
  • rosidl_typesupport_connext_cpp (Expose Connext C++ typesupport generation via rosidl generate CLI rosidl_typesupport_connext#68)
• (Nice to have) Migrate Python logic out of rosidl_cmake and into a rosidl_common package.
• Iterate on Add generalized interface generation architecture proposal design#310 if need be.

[sloretz]

@hidmic it looks like only a nice-to-have checkbox is unchecked. Is this ticket complete?