Add logs for group child notification row transient views adding

Add logs when group child notifications' row transient views are added to NotificationChildrenContainer, and when other ExpandableNotificationRows' transient views are added to the NSSL.

Bug: 281628358
Test: `adb shell settings put global systemui/buffer/NotifRenderLog
VERBOSE` and look for NotificationStackScroll tag in logcat

Change-Id: Iec4225cb44546ad2ab0e50a33dd67f3d8103f470