main-func: Reduce transitive includes

Let's move some logic from _DEFINE_MAIN_FUNCTION() and other places
in main-func.h into functions that we implement in main-func.c to
allow moving some included headers from the header to the .c file.

src/run/run.c

@@ -7,10 +7,12 @@
 #include <sys/types.h>
 
 #include "sd-bus.h"
+#include "sd-daemon.h"
 #include "sd-event.h"
 #include "sd-json.h"
 
 #include "alloc-util.h"
+#include "argv-util.h"
 #include "ask-password-agent.h"
 #include "build.h"
 #include "bus-error.h"