Set inflater factory for group summary header

This applies I093701466fecd66435b140eee415733ffa256e5e to the refactored copy of NotificationContentInflater

Bug: 371174789
Fixes: 377675742
Test: manually post group notifications and see that they have the right icon
Flag: android.app.notifications_redesign_app_icons
Flag: com.android.systemui.notification_row_content_binder_refactor
Change-Id: I0087a356d8befa4dac8531271b897c8a1dddefdd