basic: Move ratelimit logging functions to ratelimit.h

The ratelimit logging functions are only useful in a few scenarios
so let's move them to ratelimit.h instead of keeping them in the
generic log.h

src/shared/watchdog.c

@@ -15,6 +15,7 @@
 #include "fileio.h"
 #include "log.h"
 #include "path-util.h"
+#include "ratelimit.h"
 #include "string-util.h"
 #include "time-util.h"
 #include "watchdog.h"