Suggestion: Make ROS 2 nodes "composable"

[suo235]

Overview

In ROS 2, it is recommended that we write a node like a nodelet of ROS 1. Please refer to https://docs.ros.org/en/jazzy/Concepts/Intermediate/About-Composition.html .
I am ready to commit necessary changes for this suggestion.

Target branch

eloquent-devel

Note

We need to add one line to the top-level CMakeLists.txt of iris_lama to build the package.

# install location of generated cmake config files
set(ConfigPackageLocation ${CMAKE_INSTALL_LIBDIR}/${CMAKE_PROJECT_NAME}/cmake)

# dependencies
find_package(Eigen3 3.3 REQUIRED NO_MODULE)

# ##
set(CMAKE_POSITION_INDEPENDENT_CODE ON)  # We need to add this !
# ##

# the code
add_subdirectory(src)

# header files, note the "/" after include
install(DIRECTORY include/
  DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})