Only consider Settings/SystemUI for tracking last manual activation

Although including calls with ORIGIN_USER from an app could be theoretically correct, it runs counter to the desired usage -- e.g. snoozing and then resuming Bedtime from its notification will cause that mode to become the "last manually activated".

Bug: 405988332
Test: atest ZenModeHelperTest
Flag: android.app.modes_ui_tile_reactivates_last
Change-Id: Ic2bd507d2e18a339b6261123d3327bb118c5b251