New Antimalware samples, update DPI samples

DPIAwarenessPerWindow
* Center the dialog, use Segoe UI 9
* Fix compiler warnings
* Fix GDI leak in WM_CTLCOLOR_STATIC handler
* Other style issues

DPIAwarenessPerMonitor: Deleted. Superseded by the DPIAwarenessPerWindow sample.

VolumeShadowCopyServiceWriter: Clarify that the sample must match the OS bitness.

New samples: AmsiStream and AmsiProvider to demonstrate antimalware interfaces.