tree-wide: make use of new STRLEN() macro everywhere (#7639)

Let's employ coccinelle to do this for us.

Follow-up for #7625.
diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index 2344189..a7ce1a8 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -777,7 +777,7 @@
         if (S_ISLNK(st.st_mode))
                 log_debug("Skipping mode and owner fix for symlink %s.", path);
         else {
-                char fn[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
+                char fn[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
                 xsprintf(fn, "/proc/self/fd/%i", fd);
 
                 /* not using i->path directly because it may be a glob */
@@ -946,7 +946,7 @@
 static int path_set_acls(Item *item, const char *path) {
         int r = 0;
 #if HAVE_ACL
-        char fn[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
+        char fn[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
         _cleanup_close_ int fd = -1;
         struct stat st;