leon: Update CORE_BASICS/async_xxx tests to work without attrtuple.

leon-tests/CORE_BASICS/async_await2.py

 # test await expression
 
 import sys
-if sys.implementation.name == 'micropython':
+if not hasattr(sys.implementation, 'name') or sys.implementation.name == 'micropython':
     # uPy allows normal generators to be awaitables
     coroutine = lambda f: f
 else:

leon-tests/CORE_BASICS/async_for2.py

 # test waiting within "async for" aiter/anext functions
 
 import sys
-if sys.implementation.name == 'micropython':
+if not hasattr(sys.implementation, 'name') or sys.implementation.name == 'micropython':
     # uPy allows normal generators to be awaitables
     coroutine = lambda f: f
 else:

leon-tests/CORE_BASICS/async_with2.py

 # test waiting within async with enter/exit functions
 
 import sys
-if sys.implementation.name == 'micropython':
+if not hasattr(sys.implementation, 'name') or sys.implementation.name == 'micropython':
     # uPy allows normal generators to be awaitables
     coroutine = lambda f: f
 else: