feat: metadata propagation (system/user) in pynumaflow-lite

[vigith]

Closes #282

pytest -v
================================================================================================= 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 16 items

tests/test_accumulator.py::test_python_accumulator_server_and_rust_client[accumulator_stream_sorter.py] PASSED                                                                                                  [  6%]
tests/test_batchmap.py::test_python_batch_server_and_rust_client[batchmap_cat.py] PASSED                                                                                                                        [ 12%]
tests/test_batchmap.py::test_python_batch_server_and_rust_client[batchmap_cat_class.py] PASSED                                                                                                                  [ 18%]
tests/test_map.py::test_python_server_and_rust_client[map_cat.py] PASSED                                                                                                                                        [ 25%]
tests/test_map.py::test_python_server_and_rust_client[map_cat_class.py] PASSED                                                                                                                                  [ 31%]
tests/test_mapstream.py::test_python_stream_server_and_rust_client[mapstream_cat.py] PASSED                                                                                                                     [ 37%]
tests/test_mapstream.py::test_python_stream_server_and_rust_client[mapstream_cat_class.py] PASSED                                                                                                               [ 43%]
tests/test_reduce.py::test_python_reduce_server_and_rust_client[reduce_counter_class.py] PASSED                                                                                                                 [ 50%]
tests/test_reduce.py::test_python_reduce_server_and_rust_client[reduce_counter_func.py] PASSED                                                                                                                  [ 56%]
tests/test_reducestream.py::test_python_reducestream_server_and_rust_client[reducestream_counter.py] PASSED                                                                                                     [ 62%]
tests/test_session_reduce.py::test_python_session_reduce_server_and_rust_client[session_reduce_counter_class.py] PASSED                                                                                         [ 68%]
tests/test_sideinput.py::test_python_server_and_rust_client[sideinput_example.py] PASSED                                                                                                                        [ 75%]
tests/test_sink.py::test_python_sink_server_and_rust_client[sink_log.py] PASSED                                                                                                                                 [ 81%]
tests/test_sink.py::test_python_sink_server_and_rust_client[sink_log_class.py] PASSED                                                                                                                           [ 87%]
tests/test_source.py::test_python_source_server_and_rust_client[source_simple.py] PASSED                                                                                                                        [ 93%]
tests/test_sourcetransform.py::test_python_server_and_rust_client[sourcetransform_event_filter.py] PASSED                                                                                                       [100%]

================================================================================================= 16 passed in 23.21s =================================================================================================

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.91%. Comparing base (eae7222) to head (02706c2).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #305   +/-   ##
=======================================
  Coverage   93.91%   93.91%           
=======================================
  Files          66       66           
  Lines        3055     3055           
  Branches      156      156           
=======================================
  Hits         2869     2869           
  Misses        139      139           
  Partials       47       47           

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