sleep: rename sleep-config.[ch] → sleep-util.[ch]

The file long ceased to be exclusively about configuration of the sleep
operation. It contains many many calls for other purposes, hence give it
a more generic name.

src/shared/meson.build

@@ -142,7 +142,7 @@ shared_sources = files(
         'selinux-util.c',
         'serialize.c',
         'service-util.c',
-        'sleep-config.c',
+        'sleep-util.c',
         'smack-util.c',
         'socket-label.c',
         'socket-netlink.c',

src/shared/sleep-util.c

@@ -36,7 +36,7 @@
 #include "macro.h"
 #include "path-util.h"
 #include "siphash24.h"
-#include "sleep-config.h"
+#include "sleep-util.h"
 #include "stat-util.h"
 #include "stdio-util.h"
 #include "string-table.h"