chore(sonar): use ArgumentNullException.ThrowIfNull (CA1510)

Applied via `dotnet format analyzers --diagnostics CA1510 --severity info`.
Replaces `if (x == null) throw new ArgumentNullException(nameof(x));`
blocks with the one-line `ArgumentNullException.ThrowIfNull(x);` —
same behavior, same parameter name, much less noise.

6 files touched across SqlBreakdown, SqlServer, LinqToSql.

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

src/Strata.SqlTools.SqlBreakdown/Expressions/InputPropertyExpression.cs

@@ -269,10 +269,7 @@ public static class FlatDataUtils
 
     public static object GetValue(this IFlatData data, string key)
     {
-        if (data == null)
-        {
-            throw new ArgumentNullException(nameof(data));
-        }
+        ArgumentNullException.ThrowIfNull(data);
 
         if (!data.ContainsKey(key))
         {