Picker: Only emit 'change' event when value is changed. (#9029)

* isue#9027 picker emit only real user change

* issue#9027 date-picker emit change if user real change only

* issue#9027 date-picker emit change if user real change only

packages/date-picker/src/picker.vue

@@ -770,9 +770,12 @@ export default {
     },
 
     emitChange(val) {
-      this.$emit('change', val);
-      this.dispatch('ElFormItem', 'el.form.change', val);
-      this.valueOnOpen = val;
+      // determine user real change only
+      if (val !== this.valueOnOpen) {
+        this.$emit('change', val);
+        this.dispatch('ElFormItem', 'el.form.change', val);
+        this.valueOnOpen = val;
+      }
     },
 
     emitInput(val) {