move dyn_hello to examples and restore testing

boards/emlid/navio2/cross.cmake

boards/emlid/navio2/native.cmake

boards/px4/raspberrypi/cross.cmake

boards/px4/raspberrypi/native.cmake

boards/px4/sitl/default.cmake

boards/px4/sitl/rtps.cmake

boards/px4/sitl/test.cmake

platforms/posix/cmake/sitl_tests.cmake

posix-configs/SITL/init/test/test_dyn_hello

src/examples/dyn_hello/CMakeLists.txt

src/examples/dyn_hello/hello.cpp

src/platforms/posix/tests/dyn_hello/CMakeLists.txt