Fix ENTITY_AGGREGATION CF storing numeric results as strings

EntityAggregationCalculatedFieldState.toResult() serialized every metric
result via ObjectNode.put(name, JacksonUtil.toString(value)), which produces
a JSON *string* node even for numeric aggregation results (SUM/AVG/COUNT/...).
When persisted (in particular with transport.json.type_cast_enabled=false, or
for non-parsable values) the result lands in ts_kv.str_v, so server-side AVG/SUM
aggregation returns no data in widgets/queries while COUNT/MIN/MAX still return.

Serialize with JacksonUtil.valueToTree(...) so numeric results are emitted as
numeric JSON nodes (-> dbl_v/long_v), mirroring
RelatedEntitiesAggregationCalculatedFieldState. Genuine string MIN/MAX results
over string telemetry are preserved as string nodes. The instanceof Number
guard is retained (it only governs rounding).

application/src/main/java/org/thingsboard/server/service/cf/ctx/state/aggregation/single/EntityAggregationCalculatedFieldState.java

@@ -293,7 +293,7 @@ public class EntityAggregationCalculatedFieldState extends BaseCalculatedFieldSt
                     Object resultValue = argumentEntry.getValue() instanceof Number number
                             ? NumberUtils.roundResult(number.doubleValue(), precision)
                             : argumentEntry.getValue();
-                    metricsNode.put(metricName, JacksonUtil.toString(resultValue));
+                    metricsNode.set(metricName, JacksonUtil.valueToTree(resultValue));
                 }
             }
             if (!metricsNode.isEmpty()) {