feat: Reduce streaming for pynumaflow_lite

[vigith]

Fixes: #269

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.85%. Comparing base (4a381b5) to head (08f157d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #290      +/-   ##
==========================================
- Coverage   93.91%   93.85%   -0.07%     
==========================================
  Files          66       66              
  Lines        3009     3009              
  Branches      155      155              
==========================================
- Hits         2826     2824       -2     
- Misses        133      135       +2     
  Partials       50       50              

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[vigith]

(pynumaflow-lite) ➜  pynumaflow-lite git:(reduce-streaming) ✗ pytest tests/test_reducestream.py -v 2>&1
================================================================================================= test session starts =================================================================================================
platform darwin -- Python 3.13.2, pytest-8.4.2, pluggy-1.6.0 -- /Users/vigith/code/git/numaproj/numaflow-python/packages/pynumaflow-lite/.venv/bin/python3
cachedir: .pytest_cache
rootdir: /Users/vigith/code/git/numaproj/numaflow-python/packages/pynumaflow-lite
configfile: pyproject.toml
collected 1 item

tests/test_reducestream.py::test_python_reducestream_server_and_rust_client[reducestream_counter.py] PASSED                                                                                                     [100%]

================================================================================================== 1 passed in 8.29s ==================================================================================================
(pynumaflow-lite) ➜  pynumaflow-lite git:(reduce-streaming) ✗