Fix a crash in :c:func:`!_Py_Dealloc` when deallocating deeply nested container objects under memory pressure (for example after a :exc:`MemoryError`). The trashcan now also deposits objects based on a per-thread dealloc-depth counter, not only on the stack-pointer margin, so it still defers cleanup when RLIMIT_AS prevents the kernel from growing the C stack. Patch by Bhuvi.