Implement scroll_to_center method

[willmcgugan]

We have methods to scroll widgets in to view, but these tend to do as little scrolling as possible.

We may have a need to scroll something to the center. This would benefit the Tabs control.

[rodrigogiraoserrao]

Do you mind clarifying what "center" we are talking about?
With what I'm imagining in my head, I can't figure out how it would benefit the Tabs control.

[willmcgugan]

It would scroll the widgets parent so as to position the widget in the center of its container.

When move the tab selection to the right edge, you can't see what tabs are remaining. By moving the section to the center, you can see tabs in both directions.

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