It's difficult to make iterative developments when there's two
nearly-identical types that need to be kept synchronized to any change.
Rust gives us traits so we should use them instead of duplicating code.
This made it easier to make styling and layout improvements to both
instances of the segmented button.
- Removes the orientation enum in favor of two separate widgets
- Implements the spacing attribute for both widgets
- Demo is updated to display spaced variants of the widgets
