onnxruntime

Add additional test cases to check for leaks in thread pool creation / destruction (#5311)

Add additional test cases such as ThreadPoolTest.TestPoolCreation_10Iter to create and destroy thread pools to watch for any memory leaks. Running under Valgrind, these tests should show all of the data allocated being deallocated again.

Two recent issues #5176 and #5292 indicated memory leaks. The test cases help identify whether or not any of the data structures used in the thread pool are being leaked. Currently, on WSL, the only data not being de-allocated in these tests are a small number of nsync waiter objects. This behavior is as expected (the waiter objects should be held on a free list in the nsync library).