Fix refresh of "apps that can interrupt" segment

Switching from Priority Apps to None would still show the icons of the priority apps. There were several minor things wrong:
* We were keeping the AppSession when a mode switches from "priority apps" to "none", and because onResume always fires the callback, we were loading the icons.
* Even when deactivating the session, its own onResume lifecycle listener was still firing one extra time, before we had a chance to deactivate it.

Also two minor improvements to CircularIconsPreference:
* Update mLoadedIcons when we early exit due to mIconSet having no items. Mostly for testing, since the icons wouldn't be visible anyway.
* Use notifyChanged() when we get a measured view, instead of holding a reference to the view. Technically the previous code violated the "shouldn't keep references to views outside of onBindViewHolder" (although I didn't see this having an effect in practice).

Fixes: 360077747
Test: atest ZenModeAppsLinkPreferenceControllerTest
Flag: android.app.modes_ui
Change-Id: I6d4b7a344542da46f5ebfcd0774f1af27ed113ac