Add `controlWidgetVisibility` preview feature

[GerardasB]

Changes

This PR adds a controlWidgetVisibility preview feature which renders additional UI elements to allow the end user of the layout to control widget visibility.

Description	Image
Add widget and Close widget buttons in a widget action dropdown
Add widget and Close widget as separate title bar buttons
In case all widgets are hidden, a dropdown button is rendered in the bottom right of the navigation area

Additional changes:

• The dropdown menu of widgetActionDropdown will close once one of the menu items is activated.

• The labels for the buttons in the widget title bar will be rendered as tooltips, rather than using the title attribute.

  Before	After

Testing

Added a storybook story.

[GerardasB]

Add widget will auto-expand once the ellipsis is clicked on safari. This is fixed w/ iTwinUI version bump https://github.com/iTwin/appui/pull/855