Don't snooze other modes when user deactivates DND

This treats manual DND as a "regular" mode (instead of the previous special status) for this interaction. Apps that are allowed to turn DND off (which is a much smaller set in V+) still get the old behavior.

Flag: android.app.modes_ui
Test: atest ZenModeHelperTest
Bug: 326061620
Change-Id: Iaa4a1169ac54ec965cf246ac03f826849b31259e