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>

src/Strata.SqlTools.SqlBreakdown/Utilities/SqlUtils.cs

@@ -23,6 +23,7 @@ public static partial class SqlUtils
     public const string DATETIME_INSERT_FORMAT = "yyyyMMdd HH:mm:ss";
 
     private const string DEFAULT_SCHEMA = "dbo";
+    private static readonly char[] separator = new[] { ',' };
 
     #region SQL String Manipulation
 
@@ -34,7 +35,7 @@ public static partial class SqlUtils
     public static string StripColumnTableAlias(string sql)
     {
         // Break sql into words and remove "abc." from each column
-        string[] commaWords = sql.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
+        string[] commaWords = sql.Split(separator, StringSplitOptions.RemoveEmptyEntries);
         var newParts = new List<string>();
 
         foreach (string commaWord in commaWords)