UI Test: Support high dpi displays for UI testing

[jbe2277]

The unit test must run with high dpi support for the process so that UI automation (FlaUI) works correct on high dpi displays.

Microsoft documentation:

First, make the client application dpi-aware. To do this, call the SetProcessDPIAware function at startup. This function makes the entire process dpi-aware, meaning that all windows that belong to the process are unscaled.

• https://learn.microsoft.com/en-us/windows/win32/winauto/uiauto-screenscaling#scaling-in-ui-automation-clients

This PR calls SetProcessDPIAware to support this.
Note: We cannot use the application manifest approach for high dpi support as the unit test will be run by an external process.

Related issues:

• High DPI support FlaUI/FlaUI#306
• .NET 6 high dpi FlaUI/FlaUI#461