Specify which action a sanity warning is emitted for

When emitting warnings about action enablers, include the action name in the
message (unfortunately, we currently don't store the enabler section name).
This gives some context to messages that would previously look like:

  This action enabler is never used by any unit.

server/rssanity.cpp

@@ -1228,7 +1228,8 @@ bool sanity_check_ruleset_data(bool ignore_retired)
         problem = action_enabler_suggest_improvement(enabler);
         if (problem != nullptr) {
           // There is a potential for improving this enabler.
-          qCWarning(deprecations_category, "%s", problem->description);
+          qCWarning(deprecations_category, "Enabler for action %s: %s",
+                    action_id_rule_name(act), problem->description);
         }
       }
     }