bpo-42208: Call GC collect earlier in PyInterpreterState_Clear() (GH-23044)

bpo-42208: Call GC collect earlier in PyInterpreterState_Clear() (GH-23044)

The last GC collection is now done before clearing builtins and sys
dictionaries. Add also assertions to ensure that gc.collect() is no
longer called after _PyGC_Fini().

Pass also the tstate to PyInterpreterState_Clear() to pass the
correct tstate to _PyGC_CollectNoFail() and _PyGC_Fini().