Make PreferenceActivity predictive-back compatible

Bug: 380244081
Test: PreferenceActivityFlowLandscapeTest
Manual: Verify correct back navigation behaviour in PreferenceActivity (PreferenceWithHeaders test activity)
Flag: com.android.window.flags.predictive_back_default_enable_sdk_36
Change-Id: I6f4de092233644e3e04645871f466e0f17c810b8