Handle widgets added with tap-to-add in AppEventProducer

Widgets added with tap-to-add do not emit an ITEM_DROP_COMPELTED event,
so this change updates AppEventProducer to check for
WIDGET_ADD_BUTTON_TAP event so that it can emit an ACTION_PIN
event for these widgets as well.

Also moves the stats logging for tap to add to after
Launcher.addPendingItem is called, so that the PendingAddItem's container
is set to CONTAINER_DESKTOP.

Bug: 323886237
Test: manual, add widget and confirm event is produced through logging,
 and widget no longer appears in suggestions
Flag: ACONFIG com.android.launcher3.enable_widget_tap_to_add STAGING
Change-Id: Iaf46a408d05f61864a79f87b23160364b6513323