chore(sonar): hoist constant array literals to static readonly fields (CA1861)

Applied via `dotnet format analyzers --diagnostics CA1861 --severity info`,
plus manual cleanup:

- Renamed two cryptic fixer-generated field names:
  - QueryBreakdownCollection.stringArray -> SnowflakeFunctionNames (and
    inlined the now-redundant local alias)
  - ExpressionObjectTests.arg2 -> NotInValues
- Deduped three identical `separator = ['\r','\n']` fields the fixer
  emitted in the same test class (kept the first declaration; the other
  two test methods now reuse it).

8 files touched.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/Strata.SqlTools.SqlBreakdown.Tests/ExpressionTests/ExpressionObjectTests.cs

@@ -29,6 +29,8 @@ public class ExpressionObjectTests : ExpressionTestsBase
         Assert.That(paramExp.ParameterName, Is.EqualTo("MY_PARAM"));
     }
 
+    private static readonly string[] NotInValues = new[] { "value1", "value2", "value3" };
+
     private static IEnumerable<TestCaseData> ComparisonExpressionTestCases()
     {
         yield return new TestCaseData("GreaterThanOrEqual", 250, typeof(GreaterThanOrEqualToExpression))
@@ -40,7 +42,7 @@ public class ExpressionObjectTests : ExpressionTestsBase
         yield return new TestCaseData("Equals", "TestDept", typeof(EqualToExpression))
             .SetName("Equals_{m}");
 
-        yield return new TestCaseData("NotIn", new[] { "value1", "value2", "value3" }, typeof(NotInExpression))
+        yield return new TestCaseData("NotIn", NotInValues, typeof(NotInExpression))
             .SetName("NotIn_{m}");
 
         yield return new TestCaseData("Like", "%pattern%", typeof(LikeExpression))