Fixing indefinite list loading with legacy list conversion

> Sometimes apps can push remoteViews even before the widget conversation with the assumption that if will not be displayed until configuration completes.
  The widget service now maintains a flag for completed widget configuration, and disables legacy list conversion, until that.
> Simulating legacy remote-list- service behavior, onDataSetChanged is only called the first time, or if explicitely called.
> Not ignoring errors on binder call, instead passing them on to the caller
> Preventing thread straving, by actually canceling the task instead of leaving it running and just cancelling the result.

Bug: 417913555
Flag: android.appwidget.flags.remote_adapter_conversion
Test: atest RemoteViewsTest; atest AppWidgetServiceImplTest
Change-Id: I89ded0ce376d929193dbf23367b0aa7760e5052c