Replace AllocRatio ctor creation to the static field, like BaselineRatioColumn.RatioMean

Author: YegorStepanov

src/BenchmarkDotNet/Columns/BaselineAllocationRatioColumn.cs

@@ -14,6 +14,10 @@ public class BaselineAllocationRatioColumn : BaselineCustomColumn
         public override string Id => nameof(BaselineAllocationRatioColumn);
         public override string ColumnName => "Alloc Ratio";
 
+        public static readonly IColumn RatioMean = new BaselineAllocationRatioColumn();
+
+        private BaselineAllocationRatioColumn() { }
+
         public override string GetValue(Summary summary, BenchmarkCase benchmarkCase, Statistics baseline, IReadOnlyDictionary<string, Metric> baselineMetrics,
             Statistics current, IReadOnlyDictionary<string, Metric> currentMetrics, bool isBaseline)
         {

src/BenchmarkDotNet/Columns/DefaultColumnProvider.cs

@@ -66,7 +66,7 @@ public IEnumerable<IColumn> GetColumns(Summary summary)
 
                     if (HasMemoryDiagnoser(summary))
                     {
-                        yield return new BaselineAllocationRatioColumn();
+                        yield return BaselineAllocationRatioColumn.RatioMean;
                     }
                 }
             }

src/BenchmarkDotNet/Helpers/ColumnEnumHelper.cs

@@ -27,7 +27,7 @@ public static IColumnHidingRule[] ExtractRules(Column[] columns) =>
             Column.Median => ById(StatisticColumn.Median),
             Column.BaselineRatio => ById(BaselineRatioColumn.RatioMean),
             Column.BaselineRatioSD => ById(BaselineRatioColumn.RatioStdDev),
-            Column.BaselineAllocRatio => ByTypeAndName(typeof(BaselineAllocationRatioColumn), "Alloc Ratio"),
+            Column.BaselineAllocRatio => ById(BaselineAllocationRatioColumn.RatioMean),
             _ or Column.None => null
         };
 

tests/BenchmarkDotNet.Tests/ColumnEnumHelperTests.cs

@@ -22,7 +22,7 @@ public void ColumnsHiddenCorrectly()
             VerifyHiding(Column.Median, StatisticColumn.Median);
             VerifyHiding(Column.BaselineRatio, BaselineRatioColumn.RatioMean);
             VerifyHiding(Column.BaselineRatioSD, BaselineRatioColumn.RatioStdDev);
-            VerifyHiding(Column.BaselineAllocRatio, new BaselineAllocationRatioColumn());
+            VerifyHiding(Column.BaselineAllocRatio, BaselineAllocationRatioColumn.RatioMean);
         }
 
         [Theory]