GH-37651: [C#] expose ArrowArrayConcatenator.Concatenate

[davidhcoe]

Rationale for this change

New C# drivers need the ability to concatenate arrays, particularly for metadata calls.

What changes are included in this PR?

Converts a previously internal class and method to a public class and method.

Are these changes tested?

No substantive product changes were made. All tests still pass.

Are there any user-facing changes?

It exposes previously hidden functionality.

Resolves #37651

• Closes: [C#] Expose ArrowArrayConcatenator.Concatenate #37651

[github-actions]

⚠️ GitHub issue #37651 has been automatically assigned in GitHub to PR creator.

[davidhcoe]

@lidavidm - can you help with this one?

[lidavidm]

Looks like there's test failures/you may want to rebase or merge?

[lidavidm]

Oh, I guess this has to be updated to remove BindingFlags.NonPublic?

arrow/csharp/test/Apache.Arrow.Tests/ArrowArrayConcatenatorTests.cs

Lines 112 to 113 in b30d961

	private static readonly MethodInfo s_concatenateInfo = typeof(ArrayData).Assembly.GetType("Apache.Arrow.ArrowArrayConcatenator")
	.GetMethod("Concatenate", BindingFlags.Static | BindingFlags.NonPublic);

[lidavidm]

Or really: presumably reflection is no longer required for this test

[davidhcoe]

Or really: presumably reflection is no longer required for this test

good catch. I will fix the test.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 5 benchmarking runs that have been run so far on merge-commit 0d89741.

There was 1 benchmark result indicating a performance regression:

• Commit Run on arm64-t4g-linux-compute at 2023-10-06 17:56:41Z
  • dataset-read (Python) with async=True, dataset=nyctaxi_multi_parquet_s3, pre_buffer=true

The full Conbench report has more details.