Add descriptions for each line in application's CMakeLists.txt. Since
this is the first time a new user is exposed to Zephyr applications
CMakeLists.txt, it's a good time to explain why each line exists.
The descriptions must be for both new Zephyr developers with or
without CMake knowledge.
This commit also moves the comment lines from CMakeLists.txt to the
descriptions to make the file simpler.
ref. #39014
Signed-off-by: Yasushi SHOJI <yashi@spacecubics.com>
Co-authored-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
27c79d2fd6