fix(labs): update tabIndex once the element is connected to the DOM

Fix for #5398 , when hydrating tabIndex on radios and tabs, it causes a DOMException. The proposed solution suggests moving the hasConstructed property and calling the updateTabIndex method in the connectedCallback to be able to modify the tabIndex as soon as the element is connected to the DOM

labs/behaviors/focusable.ts

@@ -77,10 +77,12 @@ export function mixinFocusable<T extends MixinBase<LitElement>>(
     constructor(...args: any[]) {
       super(...args);
       this[isFocusable] = true;
-      queueMicrotask(() => {
-        this[hasConstructed] = true;
-        this[updateTabIndex]();
-      });
+    }
+
+    connectedCallback() {
+      super.connectedCallback();
+      this[hasConstructed] = true;
+      this[updateTabIndex]();
     }
 
     override attributeChangedCallback(