Log bundle expands/collapses

This adds a getBundleType() method to EntryAdapter that is only valid for bundle entries. (In theory this could be modified to also be valid for entries that are *within* bundles, but we can do that in the future if a use case ever comes up.)

Bug: 418051002
Test: manual via atomtester, ExpandableNotificationRowControllerTest
Flag: com.android.systemui.notification_bundle_ui
Change-Id: I1fa4a1c4b8516352c7ffccaf13deca49be3693a4