chore: fix lingering jest and next-server processes in monorepo (#8320)

test/helpers/stopMemoryDB.ts

@@ -0,0 +1,8 @@
+// eslint-disable-next-line no-restricted-exports
+export default async () => {
+  if (global._mongoMemoryServer) {
+    console.log('Stopping memorydb...')
+    await global._mongoMemoryServer.stop()
+    console.log('Stopped memorydb')
+  }
+}