Exclude remaining ToF tests using ThreadHelpers.cs

[schaabs]

There still appear to be some tests using ThreadHelpers which are not excluded from our stress mixes. These remaining tests need to be identified and excluded to stop polluting stress run results. Below is an example failure callstack:

libc.so.6!gsignal
libc.so.6!abort
libcoreclr.so!PROCEndProcess
libcoreclr.so!UnwindManagedExceptionPass1
libcoreclr.so!DispatchManagedException
libcoreclr.so!PreStubWorker
libcoreclr.so!ThePreStub
ThreadJoin1!Interop+mincore.CloseHandle
ThreadJoin1!System.Threading.Thread.Finalize
libcoreclr.so!FastCallFinalizeWorker
libcoreclr.so!MethodTable::CallFinalizer
libcoreclr.so!MethodTable::CallFinalizer
libcoreclr.so!FinalizerThread::DoOneFinalization
libcoreclr.so!FinalizerThread::DoOneFinalization
libcoreclr.so!FinalizerThread::FinalizeAllObjects
libcoreclr.so!FinalizerThread::FinalizerThreadWorker
libcoreclr.so!ManagedThreadBase_DispatchOuter
libcoreclr.so!ManagedThreadBase_DispatchOuter
libcoreclr.so!ManagedThreadBase_DispatchOuter
libcoreclr.so!ManagedThreadBase_DispatchOuter
libcoreclr.so!ManagedThreadBase_DispatchOuter
libcoreclr.so!ManagedThreadBase::FinalizerBase
libcoreclr.so!ManagedThreadBase::FinalizerBase
libcoreclr.so!FinalizerThread::FinalizerThreadStart
libcoreclr.so!CorUnix::CPalThread::ThreadEntry
libpthread.so.0!start_thread
libc.so.6!clone