Chore: Upgrade Vitest to v4 (#7797)

## Summary

https://vitest.dev/guide/migration.html#vitest-4

## Changes

- **What**: Update Vitest and some associated dependencies
- **What**: Fix issue with our existing mocks and mock types

## Review Focus

Double check the test updates. I tried to keep the changes minimal.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7797-Chore-Upgrade-Vitest-to-v4-2d96d73d3650810cbe3ac42d7bd6585a)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

tests-ui/tests/composables/useCachedRequest.test.ts

@@ -3,8 +3,11 @@ import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { useCachedRequest } from '@/composables/useCachedRequest'
 
 describe('useCachedRequest', () => {
-  let mockRequestFn: ReturnType<typeof vi.fn>
-  let abortSpy: ReturnType<typeof vi.fn>
+  let mockRequestFn: (
+    params: any,
+    signal?: AbortSignal
+  ) => Promise<unknown | null>
+  let abortSpy: () => void
 
   beforeEach(() => {
     vi.clearAllMocks()