GH-44911: [C#] Choose port numbers dynamically for ArrowStreamWriterTests

[CurtHagenlocher]

What changes are included in this PR?

ArrowStreamWriterTests.CanWriteToNetworkStream and ArrowStreamWriterTests.CanWriteToNetworkStreamAsync pick ports dynamically instead of hardcoding a static port.

Are these changes tested?

Yes.

Are there any user-facing changes?

No.

Resolves #44911.

• GitHub Issue: [C#] ArrowStreamWriterTests are failing  #44911

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 3 benchmarking runs that have been run so far on merge-commit c7e3122.

There were 132 benchmark results with an error:

• Commit Run on amd64-m5-4xlarge-linux at 2024-12-03 03:00:29Z
  • tpch (R) with engine=arrow, format=parquet, language=R, memory_map=False, query_id=TPCH-22, scale_factor=1
  • tpch (R) with engine=arrow, format=native, language=R, memory_map=False, query_id=TPCH-22, scale_factor=10
• and 130 more (see the report linked below)

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 1 possible false positive for unstable benchmarks that are known to sometimes produce them.