move dyn_hello to examples and restore testing

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

@@ -1,8 +0,0 @@
-px4_add_module(
-	MODULE platforms__posix__tests__dyn_hello
-	MAIN hello
-	SRCS
-		hello.cpp
-	DEPENDS
-	DYNAMIC
-	)

src/platforms/posix/tests/dyn_hello/hello.cpp

@@ -1,16 +0,0 @@
-#include <px4_log.h>
-#include <px4_app.h>
-
-extern "C" __EXPORT int hello_main(int argc, char *argv[]);
-int hello_main(int argc, char *argv[])
-{
-	PX4_INFO("Hello, I am a dynamically loaded module.");
-
-	PX4_INFO("Argv:");
-
-	for (int i = 0; i < argc; ++i) {
-		PX4_INFO("  %d: %s", i, argv[i]);
-	}
-
-	return 0;
-}