refactor: update "value" setter (#8067)

There are use-cases when the "value" setter is called early on, before the component definition and that call simply does not occur and the state is lost.
- make "value" setter "upgraded" (as it's done for the @Property decorated properties), so that the setter is available
- the setter no longer rely on the component framework-created accessors (this.options or option.disabled) because web components might not be defined yet. Instead, rely on the Light DOM - children and attributes.

packages/main/src/Select.ts

@@ -467,6 +467,8 @@ class Select extends UI5Element implements IFormElement {
  this._onMenuChange = this.onMenuChange.bind(this);
  this._attachMenuListeners = this.attachMenuListeners.bind(this);
  this._detachMenuListeners = this.detachMenuListeners.bind(this);
+
+ this._upgradeProperty("value");
  }
 
  onBeforeRendering() {
@@ -540,8 +542,11 @@ class Select extends UI5Element implements IFormElement {
  * @formEvents change liveChange
  */
  set value(newValue: string) {
- this.selectOptions.forEach(option => {
- option.selected = !!((option.value || option.textContent) === newValue);
+ const menu = this._getSelectMenu();
+ const selectOptions = Array.from(menu ? menu.children : this.children).filter(option => !option.getAttribute("disabled")) as Array<IOption>;
+
+ selectOptions.forEach(option => {
+ option.selected = !!((option.getAttribute("value") || option.textContent) === newValue);
  });
  }