fix https://github.com/flutter/flutter/issues/121493

`SegmentedButton` uses `TextButton` for each segments. When we have `MaterialTapTargetSize.padded` for `TextButton`, we make sure the minimum tap target size is 48.0( this value can be adjusted by visual density), even tough the actual button size is smaller. When `SegmentedButton` paints segments by using `MultiChildRenderObjectWidget`, it also includes the tap target size so the button that it actually draws always has the same height as the height of the tap target size.

To fix it, this PR firstly calculate the actual height of a text button in `SegmentedButton` class, then we can get the height delta if there is. Then the the value of (Segmented button render box height - the delta) would be the actual button size that we should see.

For now, we are not able to customize the min, max, fixed size in [`SegmentedButton` style](https://api.flutter.dev/flutter/material/SegmentedButton/style.html). So the standard button height is always 40 and can only be customized by `style.visualDensity` and `style.tapTargetSize`; `SegmentedButton` only simulates the `TextButton` behavior when `TextButton`'s height is its default value.

![Screenshot 2024-01-25 at 11 45 42 AM](https://github.com/flutter/flutter/assets/36861262/7451fa96-6d45-4cd3-a894-ca71e776c8ef)

https://github.com/flutter/flutter/assets/36861262/15ca6034-e6e0-4cc6-8fe3-808b4bd6a920