Improve coroutine timeout handling

[deathaxe]

resolves #294

This PR...

1. adds class-level timeout_ms attribute to customize runtime of asyncio coroutines.

   Example:

      class MyAsyncTestCase(AsyncTestCase):
          timeout_ms=10000

2. uses timeout_ms argument from test_... coroutines to cutomize test case runtime.

   Example:

      async def test_anything(self, timeout_ms=10000):
          ...

3. raises TimeoutError within context of currently awaited asynchronous coroutine to ensure valuable tracebacks being printed.

   Example:

   test_coroutine (test_asyncio_timeout.MyAsyncTestCaseA.test_coroutine) ... ERROR
   
   ======================================================================
   ERROR: test_coroutine (test_asyncio_timeout.MyAsyncTestCaseA.test_coroutine)
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "<ST>\Data\Packages\UnitTesting\unittesting\core\py313\case.py", line 120, in run
       outcome.expecting_failure = False
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "<ST>\Data\Packages\UnitTesting\unittesting\core\py313\case.py", line 71, in _callMaybeCoro
     File "<ST>\Data\Packages\UnitTesting\tests\test_asyncio_timeout.py", line 23, in test_coroutine
       await a_coro(self)
     File "<ST>\Data\Packages\UnitTesting\tests\test_asyncio_timeout.py", line 7, in a_coro
       await a_coro2(test)
     File "<ST>\Data\Packages\UnitTesting\tests\test_asyncio_timeout.py", line 11, in a_coro2
       await a_coro3(test)
     File "<ST>\Data\Packages\UnitTesting\tests\test_asyncio_timeout.py", line 15, in a_coro3
       await asyncio.sleep(10.0)
     File "./python3.14/asyncio/tasks.py", line 702, in sleep
   TimeoutError: Task not completed within 4.50 seconds.
   
   ----------------------------------------------------------------------
   Ran 1 test in 4.667s
   
   FAILED (errors=1)
   

[rwols]

I didn’t know this .throw was possible. Very cool!