Do not hardcode Margin and VerticalAlignment on data grid text column

src/Avalonia.Controls.DataGrid/DataGridTextColumn.cs

@@ -19,8 +19,6 @@ namespace Avalonia.Controls
     /// </summary>
     public class DataGridTextColumn : DataGridBoundColumn
     {
-        private const string DATAGRID_TextColumnCellTextBlockMarginKey = "DataGridTextColumnCellTextBlockMargin";
-
         /// <summary>
         /// Initializes a new instance of the <see cref="T:Avalonia.Controls.DataGridTextColumn" /> class.
         /// </summary>
@@ -178,8 +176,7 @@ namespace Avalonia.Controls
         {
             TextBlock textBlockElement = new TextBlock
             {
-                [!Layoutable.MarginProperty] = new DynamicResourceExtension(DATAGRID_TextColumnCellTextBlockMarginKey),
-                VerticalAlignment = VerticalAlignment.Center
+                Name = "CellTextBlock"
             };
 
             SyncProperties(textBlockElement);

src/Avalonia.Controls.DataGrid/Themes/Default.xaml

@@ -29,6 +29,10 @@
       </ControlTemplate>
     </Setter>
   </Style>
+  <Style Selector="DataGridCell > TextBlock#CellTextBlock">
+    <Setter Property="Margin" Value="{DynamicResource DataGridTextColumnCellTextBlockMargin}" />
+    <Setter Property="VerticalAlignment" Value="Center" />
+  </Style>
 
   <Style Selector="DataGridColumnHeader">
     <Setter Property="Foreground" Value="{DynamicResource ThemeForegroundBrush}" />

src/Avalonia.Controls.DataGrid/Themes/Fluent.xaml

@@ -145,6 +145,11 @@
     </Setter>
   </Style>
 
+  <Style Selector="DataGridCell > TextBlock#CellTextBlock">
+    <Setter Property="Margin" Value="{DynamicResource DataGridTextColumnCellTextBlockMargin}" />
+    <Setter Property="VerticalAlignment" Value="Center" />
+  </Style>
+  
   <Style Selector="DataGridCell /template/ Rectangle#CurrencyVisual">
     <Setter Property="IsVisible" Value="False" />
   </Style>