Clean up flag notification_async_hybrid_view_inflation 3

The impact of this flag is particularly wide, so breaking down the flag
removal by method for code robustness and easier review. This change
cleans the AsyncHybridViewInflation.isEnabled()

Clean up flag:
com.android.systemui.notification_async_hybrid_view_inflation

Bug: 409612328
Test: SingleLineViewInflaterTest, SingleLineViewBinderTest,
NotifUiAdjustmentProviderTest
Flag: EXEMPT flag cleanup

Change-Id: Iec721ee40bc33e5330ce10afbe34bcf6f7cee502