Tests fail when using Python 3.14

[martincostello]

While working on .NET 11 support for the OpenTelemetry .NET SDK, which uses this test suite as part of its CI validation, I found that the tests don't work on Python 3.14, which is included in the .NET 11 SDK container images.

You can see such a failure here from #580:

======================================================================
ERROR: setUpModule (test)
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Traceback (most recent call last):
  File "/home/runner/work/trace-context/trace-context/test/test.py", line 34, in setUpModule
    server = server or TestServer(host = '127.0.0.1', port = 7777, timeout = 3)
                       ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/trace-context/trace-context/test/server.py", line 78, in __init__
    self.loop = asyncio.get_event_loop()
                ~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/hostedtoolcache/Python/3.14.3/x64/lib/python3.14/asyncio/events.py", line 715, in get_event_loop
    raise RuntimeError('There is no current event loop in thread %r.'
                       % threading.current_thread().name)
RuntimeError: There is no current event loop in thread 'MainThread'.

----------------------------------------------------------------------
Ran 33 tests in 0.057s

I have a patch for this locally that seems to work, so I'll look to push up a fix.

[SergeyKanzhelev]

I have a patch for this locally that seems to work, so I'll look to push up a fix.

yes please. Thank you!

[martincostello]

#582