dbus-cgroup: add BPFProgram= dbus support

- Handle BPFProgram= property in string format
"<bpf_attach_type>:<bpffs_path>", e.g. egress:/sys/fs/bpf/egress-hook.
- Add dbus getter to list foreign bpf programs attached to a cgroup.

src/systemctl/systemctl-show.c

@@ -1694,6 +1694,23 @@ static int print_property(const char *name, const char *expected_value, sd_bus_m
 
                         return 1;
 
+                } else if (streq(name, "BPFProgram")) {
+                        const char *a, *p;
+
+                        r = sd_bus_message_enter_container(m, SD_BUS_TYPE_ARRAY, "(ss)");
+                        if (r < 0)
+                                return bus_log_parse_error(r);
+
+                        while ((r = sd_bus_message_read(m, "(ss)", &a, &p)) > 0)
+                                bus_print_property_valuef(name, expected_value, value, "%s:%s", a, p);
+                        if (r < 0)
+                                return bus_log_parse_error(r);
+
+                        r = sd_bus_message_exit_container(m);
+                        if (r < 0)
+                                return bus_log_parse_error(r);
+
+                        return 1;
                 }
 
                 break;