refactor: revert set value order change and validate on value change

Author: ugur-vaadin

vaadin-date-time-picker-flow-parent/vaadin-date-time-picker-flow/src/main/java/com/vaadin/flow/component/datetimepicker/DateTimePicker.java

@@ -354,7 +354,7 @@ public DateTimePicker(LocalDateTime initialDateTime, Locale locale) {
     }
 
     private void addValidationListeners() {
-        getElement().addEventListener("change", e -> validate(true));
+        addValueChangeListener(e -> validate());
         getElement().addEventListener("unparsable-change", e -> validate(true));
     }
 
@@ -379,9 +379,11 @@ public void setValue(LocalDateTime value) {
         var shouldFireValidationStatusChangeEvent = oldValue == null
                 && value == null
                 && (isInputUnparsable() || isInputIncomplete());
-        synchronizeChildComponentValues(value);
-        validate(shouldFireValidationStatusChangeEvent);
         super.setValue(value);
+        synchronizeChildComponentValues(value);
+        if (shouldFireValidationStatusChangeEvent) {
+            validate(true);
+        }
     }
 
     /**