Notification Minimalism Prototype

When the flag is enabled:
* Cap notifications on lock screen at 1, excluding the UMO
* Act as if LOCK_SCREEN_SHOW_ONLY_UNSEEN_NOTIFICATIONS is Enabled

Bug: 330387368
Test: atest SystemUITests
Flag: ACONFIG com.android.systemui.notification_minimalism_prototype DEVELOPMENT
Change-Id: Ibc47fd1858b62abcab557198ebaf5f2f4587bf11