WMI MI_ApplicationFT struct is hard to use

Related: microsoft/windows-rs#1572

WMI APIs such as MI_Application_NewSession are header-only. (Nearly all of them are.) That's not a problem per se but in this case, after calling MI_Application_InitializeV1 you get back a function table defined as such:

typedef struct _MI_ApplicationFT
{
    MI_Result (MI_CALL *Close)(
        _Inout_     MI_Application *application);

    MI_Result (MI_CALL *NewSession)(
        _In_     MI_Application *application,
        _In_opt_z_ const MI_Char *protocol,
        _In_opt_z_ const MI_Char *destination,
        _In_opt_ MI_DestinationOptions *options,
        _In_opt_ MI_SessionCallbacks *callbacks,
        _Outptr_opt_result_maybenull_ MI_Instance **extendedError,
        _Out_    MI_Session *session);

    MI_Result (MI_CALL *NewHostedProvider)(
        _In_     MI_Application *application,
        _In_z_     const MI_Char *namespaceName,
        _In_z_     const MI_Char *providerName,
        _In_     MI_MainFunction mi_Main,
        _Outptr_opt_result_maybenull_ MI_Instance **extendedError,
        _Out_    MI_HostedProvider *provider
        );

   // ...
}

Metadata currently houses a table of difficult to use bare IntPtrs.

public struct MI_ApplicationFT
{
	public IntPtr Close;
	public IntPtr NewSession;
	public IntPtr NewHostedProvider;
	public IntPtr NewInstance;
	public IntPtr NewDestinationOptions;
	public IntPtr NewOperationOptions;
	public IntPtr NewSubscriptionDeliveryOptions;
	public IntPtr NewSerializer;
	public IntPtr NewDeserializer;
	public IntPtr NewInstanceFromClass;
	public IntPtr NewClass;
}