apacheGH-41164: [C#] Fix concatenation of sliced arrays (apache#41245)

### Rationale for this change

Makes array concatenation work correctly when the input arrays have been sliced.

### What changes are included in this PR?

* Updates the array concatenation tests so that the `TestDataGenerator` can generate test cases with sliced input arrays. To avoid too much duplicated logic, I've added a new `GenerateTestData<TArray, TArrayBuilder>` method that works with builders that are not `IArrowArrayBuilder<T, TArray, TArrayBuilder>`, and simplified a lot of the data generation by using this new method. Only struct and union array test data generation still needs to duplicate the logic in `GenerateTestData`.
* Fixes `ArrayDataConcatenator` logic to handle sliced input arrays

### Are these changes tested?

Yes, I've added a new test for this.

### Are there any user-facing changes?

Yes, this is a user-facing bug fix.
* GitHub Issue: apache#41164

Authored-by: Adam Reeve <adreeve@gmail.com>
Signed-off-by: Curt Hagenlocher <curt@hagenlocher.org>

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

@@ -404,11 +404,15 @@ public void Visit(UnionType type)
 
                     for (int j = 0; j < dataList.Count; j++)
                     {
+                        bool includeInResult = IncludeInResult(i, j);
                         byte index = (byte)Math.Min(j % 3, 1);
                         int? intValue = (index == 1) ? dataList[j] : null;
                         string stringValue = (index == 1) ? null : dataList[j]?.ToString();
                         typeBuilder.Append(index);
-                        typeResultBuilder.Append(index);
+                        if (includeInResult)
+                        {
+                            typeResultBuilder.Append(index);
+                        }
 
                         if (isDense)
                         {