Improve performance and reduce memory use and reduce array allocations by reusing char[] (#9166)

* Reduce array allocations by reusing char[]

* don't hide .Equals()

* Reduce memory use by reducing array allocations

* Revert "Reduce memory use by reducing array allocations"

This reverts commit faf6b60234167f5443435243eb52187ab07d514c.

* reuse char[] for string.split() to avoid params [] allocation

src/Umbraco.Core/Persistence/SqlSyntax/SqlSyntaxProviderBase.cs

@@ -403,7 +403,7 @@ namespace Umbraco.Core.Persistence.SqlSyntax
             var columns = string.IsNullOrEmpty(columnDefinition.PrimaryKeyColumns)
                 ? GetQuotedColumnName(columnDefinition.Name)
                 : string.Join(", ", columnDefinition.PrimaryKeyColumns
-                                                    .Split(new[] { ',', ' ' }, StringSplitOptions.RemoveEmptyEntries)
+                                                    .Split(Constants.CharArrays.CommaSpace, StringSplitOptions.RemoveEmptyEntries)
                                                     .Select(GetQuotedColumnName));
 
             var primaryKeyPart = string.Concat("PRIMARY KEY", columnDefinition.IsIndexed ? " CLUSTERED" : " NONCLUSTERED");