Re-implementation of depreciated class and functions in capture.py

[emmseth]

Closes #703

[Koen1999]

I wanted to check if this PR added support for Python 3.14, but sadly it introduces a new issue:

  File "/usr/local/lib/python3.14/site-packages/pyshark/__init__.py", line 13, in <module>
    from pyshark.capture.live_capture import LiveCapture
  File "/usr/local/lib/python3.14/site-packages/pyshark/capture/live_capture.py", line 7, in <module>
    from pyshark.capture.capture import Capture
  File "/usr/local/lib/python3.14/site-packages/pyshark/capture/capture.py", line 19, in <module>
    from pyshark.capture.child_watching import NewUnixDefaultEventPolicy
  File "/usr/local/lib/python3.14/site-packages/pyshark/capture/child_watching.py", line 122, in <module>
    class NewUnixDefaultEventPolicy(events.BaseDefaultEventLoopPolicy):
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: module 'asyncio.events' has no attribute 'BaseDefaultEventLoopPolicy'