Slider control is asymmetrical on 125% DPI

### Describe the bug

The Slider control has different paddings from the central blue dot to margins on 125% DPI

See the screenshot below, the lengths of green and orange lines are different, 6 and 7 pixels.

This cause subtle feel of unbalanced and distirbing look.

### Why is this important?

This cause feeling that an app UI is not perfect.

### Steps to reproduce the bug

Set DPI to 125%.
See the Slider control in WinUI 3 Gallery app.

### Actual behavior

Paddings around central blue dot are different

### Expected behavior

Paddings around central blue dot are equal

### Screenshots

### NuGet package version

WinUI 3 - Windows App SDK 1.8.3: 1.8.251106002

### Windows version

Windows 10 (21H2): Build 19044

### Additional context

_No response_

Reproduce the Slider control in the WinUI 3 Gallery with display scaling set to 125%, using the reported Windows App SDK 1.8.3 environment. Inspect the Slider control's layout and styling, then verify that the padding from the central blue dot to both margins is equal at that scale.

Written by the indexing model from the issue text.