Fill a preference's ${setting:} from its manifest default (hq ADR 0262)

Without a default, a running module could never gain a setting: the file asking for it
failed to compose until set, and the key was refused as stray until a file asked for it.
Defaults sit under the mesh's and the node's settings, never merge into a JSON file, are
refused for the operator's own values, and settings shows each value's source.

cmd/mesh-controller/plan.go

@@ -1425,7 +1425,7 @@ func servedOnNode(ctx context.Context, inv *inventory.Inventory, node string,
 	}
 	serves := catalogue.ServedOn(m, provision, ports)
 	if len(serves) > 0 {
-		serves, err = catalogue.Settle(serves, layers)
+		serves, err = catalogue.Settle(serves, catalogue.WithDefaults(m, layers))
 		if err != nil {
 			return nil, err
 		}