core: add {State,Cache,Log,Configuration}Directory= (#6384)

This introduces {State,Cache,Log,Configuration}Directory= those are
similar to RuntimeDirectory=. They create the directories under
/var/lib, /var/cache/, /var/log, or /etc, respectively, with the mode
specified in {State,Cache,Log,Configuration}DirectoryMode=.

This also fixes #6391.

src/basic/exit-status.c

@@ -151,6 +151,18 @@ const char* exit_status_to_string(int status, ExitStatusLevel level) {
 
                 case EXIT_KEYRING:
                         return "KEYRING";
+
+                case EXIT_STATE_DIRECTORY:
+                        return "STATE_DIRECTORY";
+
+                case EXIT_CACHE_DIRECTORY:
+                        return "CACHE_DIRECTORY";
+
+                case EXIT_LOGS_DIRECTORY:
+                        return "LOGS_DIRECTORY";
+
+                case EXIT_CONFIGURATION_DIRECTORY:
+                        return "CONFIGURATION_DIRECTORY";
                 }
         }