refactor: improve visible condition of global search component (#5976)

#### What type of PR is this?

/area ui
/kind improvement
/milestone 2.16.x

#### What this PR does / why we need it:

优化 Console 的全局搜索对话框显示逻辑，改为未开启时不渲染组件。

#### Does this PR introduce a user-facing change?

```release-note
None
```

ui/console-src/layouts/BasicLayout.vue

@@ -295,7 +295,10 @@ onMounted(() => {
       </Teleport>
     </div>
   </div>
-  <GlobalSearchModal v-model:visible="globalSearchVisible" />
+  <GlobalSearchModal
+    v-if="globalSearchVisible"
+    @close="globalSearchVisible = false"
+  />
   <LoginModal />
 </template>