Managed virtual method table property

[jtschuster]

Includes #82657, so wait until that's merged to look.

Adds GenerateIIUnknownInterfaceTypeImplementation method to generate the implementation of IIUnknownInterfaceType for the Com interface shown below. It always uses a guid of all 0's.

static Guid IIUnknownInterfaceType.Iid => new Guid("00000000-0000-0000-0000-000000000000");

private static readonly void** m_vtable = (void**)RuntimeHelpers.AllocateTypeAssociatedMemory(typeof(<InterfaceType>), sizeof(void*) * <numberOfInterfaceMethods + 3>);

static void** IIUnknownInterfaceType.ManagedVirtualMethodTable
{
    get
    {
        if (m_vtable[0] == null)
        {
            nint v0, v1, v2;
            ComWrappers.GetIUnknownImpl(out v0, out v1, out v2);
            m_vtable[0] = (void*)v0;
            m_vtable[1] = (void*)v1;
            m_vtable[2] = (void*)v2;
            Native.PopulateManagedVirtualMethodTable(m_vtable);
        }
         return m_vtable;
    }
}

Also adds a definition of an interface with [GeneratedComInterface] to easily view the output of the generator in VS, and as a basis for functionality tests.

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Issue Details

---

Includes #82657, so wait until that's merged to look.

Adds GenerateIIUnknownInterfaceTypeImplementation method to generate the implementation of IIUnknownInterfaceType for the Com interface shown below. It always uses a guid of all 0's.

static Guid IIUnknownInterfaceType.Iid => new Guid("00000000-0000-0000-0000-000000000000");

private static readonly void** m_vtable = (void**)RuntimeHelpers.AllocateTypeAssociatedMemory(typeof(<InterfaceType>), sizeof(void*) * <numberOfInterfaceMethods + 3>);

static void** IIUnknownInterfaceType.ManagedVirtualMethodTable
{
    get
    {
        if (m_vtable[0] == null)
        {
            nint v0, v1, v2;
            ComWrappers.GetIUnknownImpl(out v0, out v1, out v2);
            m_vtable[0] = (void*)v0;
            m_vtable[1] = (void*)v1;
            m_vtable[2] = (void*)v2;
            Native.PopulateManagedVirtualMethodTable(m_vtable);
        }
         return m_vtable;
    }
}

Also adds a definition of an interface with [GeneratedComInterface] to easily view the output of the generator in VS, and as a basis for functionality tests.

Author:	jtschuster
Assignees:	jtschuster
Labels:	area-System.Runtime.InteropServices
Milestone:	-

[AaronRobinsonMSFT]

It always uses a guid of all 0's.

@jtschuster This is fine for a draft PR but all 0's represents GUID_NULL which is an invalid interface ID. I would hardcode a few GUID values and then also have at least a test that uses a randomly generated one.

[jtschuster]

This is mostly a subset of #83055