Fix broken WmTests

- Adds missing import for PackageManager
- Reverts call to `newWindowBuilder`

Bug: 450088648
Test: atest WindowManagerServiceTests
Flag: EXEMPT TEST_ONLY
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:5714f42fb1a1ba2fc2c04d56bb979e07fe19b8b2
Merged-In: Ia7efae42741687c69804e5ff97e0f0a29a7b626c
Change-Id: Ia7efae42741687c69804e5ff97e0f0a29a7b626c