Adds the ability to apply a layout to the segment button in order to better match the Material Design spec, updates the design and UI to match the spec more, and separates the segment button styles back into the proper directory.
- moves the segment button css back into segment-button directory
- updates the design to match the MD spec better
- adds layout property to match MD spec
- adds custom properties for better styling
- allows for overscroll / scrolling tabs via scrollable attribute
- changes the indicator to a div - will need to animate it
- updates e2e tests and add spec test
fixes#16232fixes#16081
references #14853
BREAKING CHANGES
Segment Button now requires the text to be wrapped in an `ion-label` element for improved styling.
*Old usage:*
```html
<ion-segment-button>
Item One
</ion-segment-button>
```
*New usage:*
```html
<ion-segment-button>
<ion-label>Item One</ion-label>
</ion-segment-button>
```
Note: this will not technically break your app, but the styles may look wrong.
