DataGridViewComboBoxCell has multiple layout issues when entering edit mode

### .NET version

.NET 11.0.100-preview.7.26365.114 + Private dlls built from Net11/Integration-3 branch of https://github.com/KlausLoeffelmann/winforms repo

### Did it work in .NET Framework?

Not tested/verified

### Did it work in any of the earlier releases of .NET Core or .NET 5+?

Not support, new feature of https://github.com/dotnet/winforms/pull/14768

### Issue description

When `VisualStylesMode `is set to `NET11`, the embedded `ComboBox` editor used by `DataGridViewComboBoxCell` exhibits several layout/rendering issues while editing:

- The rounded drop-down button is shifted to the left instead of aligning with the right edge of the editor.
- An unexpected vertical scrollbar appears to the right of the drop-down button.
- The drop-down list is slightly offset from the editing control instead of opening flush beneath it.

These issues make the embedded ComboBox editor appear misaligned and visually inconsistent.

https://github.com/user-attachments/assets/5aa52c39-b605-445f-8c78-44e296546c91

### Steps to reproduce

1. Create a new WinForms application targeting .NET 11.
2. Set the Form's `VisualStylesMode` to `NET11`.
3. Add a `DataGridView` to the Form.
4. Add a `DataGridViewComboBoxColumn` and populate it with several items.
5. Run the application.
6. Click a cell in the `DataGridViewComboBoxColumn` to enter edit mode.
7. Open the drop-down list.