Closes #246160

Adds a new option, workbench.editor.titleScrollbarVisibility, to control the visibility of the scrollbars used for tabs and breadcrumbs in the editor title area. Possible options are auto, visible, and hidden.

This option mirrors the behavior of an existing option, editor.scrollbar.horizontal.

How to test:

• Use all default options.
• Open many tabs in the editor until a scrollbar appears. Alternatively, shrink the width of the window.
• Open a file that creates a long breadcrumb that requires scrolling. See the example file below.
• Observe that by default, the scrollbars appear only when you hover.
• Change the new workbench.editor.titleScrollbarVisibility option to visible or hidden and test the behavior.

function superDuperLongOuterFunctionNameToMakeTheBreadcrumbHaveToScroll() {
  function superLongInnerFunctionNameToMakeTheBreadcrumbHaveToScroll() {
  	
  }
}

Screen recording that demonstrates the new option: