[release/8.0] Use strategy in StrategyBasedComWrappers.ComputeVtables (#92250)

* Use strategy in StrategyBasedComWrappers.ComputeVtables

We didn't actually use the strategy object here, so users like WinForms can't actually use it.

* Update src/libraries/System.Runtime.InteropServices/src/System/Runtime/InteropServices/Marshalling/StrategyBasedComWrappers.cs

Co-authored-by: Jackson Schuster <[email protected]>

---------

Co-authored-by: Jeremy Koritzinsky <[email protected]>
Co-authored-by: Jackson Schuster <[email protected]>

Author: 3 people

src/libraries/System.Runtime.InteropServices/src/System/Runtime/InteropServices/Marshalling/StrategyBasedComWrappers.cs

@@ -76,7 +76,7 @@ static IIUnknownInterfaceDetailsStrategy GetInteropStrategy()
         /// <inheritdoc cref="ComWrappers.ComputeVtables" />
         protected sealed override unsafe ComInterfaceEntry* ComputeVtables(object obj, CreateComInterfaceFlags flags, out int count)
         {
-            if (obj.GetType().GetCustomAttribute(typeof(ComExposedClassAttribute<>)) is IComExposedDetails details)
+            if (GetOrCreateInterfaceDetailsStrategy().GetComExposedTypeDetails(obj.GetType().TypeHandle) is { } details)
             {
                 return details.GetComInterfaceEntries(out count);
             }