Fix for incorrect release of CCW holder

[kant2002]

Fixes: microsoft/CsWinRT#1321 Make ComWrappers in C# work closely with how C++ part works

• RefCount => curr is plain typo
• Do not destroy wrappers if ref count == 0. That's mimic how CoreCLR work. MOWHolder's finilizer calls Destroy
• Also discover 2 tests which are plainly wrong, since they do not work under CoreCLR

[kant2002]

/cc @dotnet/interop-contrib

[kant2002]

Released actually here

runtime/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/ComWrappers.NativeAot.cs

Lines 282 to 287 in e21242a

	~ManagedObjectWrapperHolder()
	{
	// Release GC handle created when MOW was built.
	_wrapper->Destroy();
	NativeMemory.Free(_wrapper);
	}

[jkoritzinsky]

LGTM other than what looks like some remains of the dead code in the smoke test.

[Sergio0694]

Would this meet the bar for a .NET 7 servicing release, or will this be .NET 8 only?

[jkoritzinsky]

After looking into this more, there's a more serious issue here that needs to be fixed before this is merged in. The ComWrappers implementation on NativeAOT uses a strong GC handle to hold the managed object alive from the MOW. With this change, the managed object will never be released, as the MOW will hold a strong ref to the managed object that will not be released until the MOW is destroyed, which won't happen until after the managed object is released since the MOW is kept alive by the managed object through a ConditionalWeakTable.

I believe we need to change the ComWrappers implementation to use ref-counted handles in this case. NativeAOT has partial support for ref-counted handles, but it might need to be extended slightly to work as well as possible.