perf: hide anonymousUser in user filter dropdown list (#891)

#### What type of PR is this?

/kind improvement

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

在用户条件筛选框中隐藏匿名用户。

#### Which issue(s) this PR fixes:

Fixes halo-dev/halo#3407

#### Screenshots:

<img width="864" alt="image" src="https://user-images.githubusercontent.com/21301288/221490795-eaf9c515-e487-4d76-87dd-f0010415360e.png">

#### Special notes for your reviewer:

None

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

```release-note
None
```

src/modules/system/users/composables/use-user.ts

@@ -17,10 +17,14 @@ export function useUserFetch(options?: {
   const users = ref<User[]>([] as User[]);
   const loading = ref(false);
 
+  const ANONYMOUSUSER_NAME = "anonymousUser";
+
   const handleFetchUsers = async () => {
     try {
       loading.value = true;
-      const { data } = await apiClient.extension.user.listv1alpha1User();
+      const { data } = await apiClient.extension.user.listv1alpha1User({
+        fieldSelector: [`name!=${ANONYMOUSUSER_NAME}`],
+      });
       users.value = data.items;
     } catch (e) {
       console.error("Failed to fetch users", e);