feat: ion-segment - Add horizontal scroll buttons

# Feature Request

**Ionic version:**

[x] **4.x**

**Describe the Feature Request**
When having a larger number of ion-segment items that cannot be fitted on screen, we can enable property "scrollable", however it doesn't have any indication to the user that there are more elements / segments that are not showing. In other words, the user doesn't know that there are segments to scroll to that are not currently showing on the screen.

**Describe Preferred Solution**
Ideally, a property gets added to show scrollable buttons on far left and far right to indicate to the user that there are items hidden to the right or to the left. Example from the material ui library: https://material-ui.com/components/tabs/#forced-scroll-buttons

**Describe Alternatives** N/A

**Related Code** N/A

**Additional Context** N/A

Start by locating the ion-segment implementation and its existing scrollable behavior. Review how segment items overflow the screen and determine the expected interaction for buttons at the far left and right. Done means users can discover and reach hidden segments in both directions, with behavior matching the requested Material UI example.

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