Add logcat logging for smart suggestions.

In cases where smart suggestions in notifications are not shown we want
to be able to debug why the suggestions are not shown.
With this CL we add logcat logs (conditional on log tags) to be able to
debug suggestions when we have physical access to a device.

Bug: 122895786
Test: 'adb shell setprop log.tag.ExtAssistant',
'adb shell setprop log.tag.NotificationContentView' and ensure the logs
are displayed when showing a notification.

Change-Id: I77a3fbc2b1b325d97d8e2306ffbcce17c84129f8