Friendly overloads of functions with an HDC parameter should accept `SafeHandle`

EnumDisplayMonitors could before called this way:

Windows.Win32.PInvoke.EnumDisplayMonitors(null, null, proc, 0);

Now the compiler complains:

Argument 1: cannot convert from '' to 'Windows.Win32.Graphics.Gdi.HDC'

I checked the two version and it seems 0.3.18-beta does not create the SafeHandle version anymore (see below the generated code for the two version). Is this a bug or was this intended?

0.2.46-beta

internal static unsafe winmdroot.Foundation.BOOL EnumDisplayMonitors(SafeHandle hdc, winmdroot.Foundation.RECT? lprcClip, winmdroot.Graphics.Gdi.MONITORENUMPROC lpfnEnum, winmdroot.Foundation.LPARAM dwData)

internal static extern unsafe winmdroot.Foundation.BOOL EnumDisplayMonitors(winmdroot.Graphics.Gdi.HDC hdc, [Optional] winmdroot.Foundation.RECT* lprcClip, winmdroot.Graphics.Gdi.MONITORENUMPROC lpfnEnum, winmdroot.Foundation.LPARAM dwData);

0.3.18-beta

internal static unsafe winmdroot.Foundation.BOOL EnumDisplayMonitors(winmdroot.Graphics.Gdi.HDC hdc, winmdroot.Foundation.RECT? lprcClip, winmdroot.Graphics.Gdi.MONITORENUMPROC lpfnEnum, winmdroot.Foundation.LPARAM dwData)

internal static extern unsafe winmdroot.Foundation.BOOL EnumDisplayMonitors(winmdroot.Graphics.Gdi.HDC hdc, [Optional] winmdroot.Foundation.RECT* lprcClip, winmdroot.Graphics.Gdi.MONITORENUMPROC lpfnEnum, winmdroot.Foundation.LPARAM dwData);

Originally posted by @msedi in https://github.com/microsoft/CsWin32/issues/1022#issuecomment-1722834688

Start at the generator entry point for the EnumDisplayMonitors overloads and compare the generated output described for versions 0.2.46-beta and 0.3.18-beta. Trace how HDC parameters are classified, then locate or add a regression test showing that the friendly overload accepts SafeHandle and permits the null call shown in the issue.