Fix ShuffleThunk cache heap (#105480)

There was a problem with using heap from the related LoaderAllocator for
shuffle thunk cache heap. I have tested it again and it seems that the
issue is gone.

So I am removing the workaround, making the cache use LoaderAllocator
local heap.

Close #55697

src/coreclr/vm/loaderallocator.cpp

@@ -1734,11 +1734,7 @@ void AssemblyLoaderAllocator::Init(AppDomain* pAppDomain)
     LoaderAllocator::Init((BaseDomain *)pAppDomain);
     if (IsCollectible())
     {
-        // TODO: the ShuffleThunkCache should really be using the m_pStubHeap, however the unloadability support
-        // doesn't track the stubs or the related delegate classes and so we get crashes when a stub is used after
-        // the AssemblyLoaderAllocator is gone (the stub memory is unmapped).
-        // https://github.com/dotnet/runtime/issues/55697 tracks this issue.
-        m_pShuffleThunkCache = new ShuffleThunkCache(SystemDomain::GetGlobalLoaderAllocator()->GetExecutableHeap());
+        m_pShuffleThunkCache = new ShuffleThunkCache(m_pStubHeap);
     }
 }