Fix DataGrid Fluent control style

[dipeshmsft]

Description

This issue is supposed to track the DataGrid Fluent style issues. Apart from the things mentioned in the parent issue #10393, as part of this issue we will track the following fluent issues as well :

• Inconsistent Header Styles for Data Grid #8678
• Fluent2 DataGrid Style Doesn't Match Theme #9562
• Fluent2 datagrid cell style based on DefaultDataGridCellStyle #10351
• Fluent2: DataGrid ColumnHeader is Not Sortable #10400