Add test for multiple views

Test: atest android.view.contentcapture.LoginTest#testNotifyVirtualChildrenAppearedWithCustomView_100
Flag: android.view.contentcapture.flags.enable_export_assist_virtual_node_to_ccapi
Bug: 430421182
Change-Id: I43002102f44352da9f897773353b82c5d7cccdea