analyze: extend the dump command to accept patterns

The new function DumpPatterns() can be used to limit (drastically) the size of
the data returned by PID1. Hence the optimization of serializing data into a
file descriptor should be less relevant than having the possibility to limit
the data when communicating with the service manager remotely.

NB: when passing patterns, the dump command omits the version of the manager as
well as the features and the timestamps.

src/core/execute.c

@@ -919,7 +919,7 @@ static int ask_for_confirmation(const ExecContext *context, const char *vc, Unit
                                u->id, u->description, cmdline);
                         continue; /* ask again */
                 case 'j':
-                        manager_dump_jobs(u->manager, stdout, "  ");
+                        manager_dump_jobs(u->manager, stdout, /* patterns= */ NULL, "  ");
                         continue; /* ask again */
                 case 'n':
                         /* 'n' was removed in favor of 'f'. */