Test for #1749

• Windows @isidorn
• Linux @Tyriar
• Mac @rebornix

You can now switch between vertical and horizontal layout for opened editors. Verify

• you can switch the layout from the View menu, command palette and "opened editors" view
• the choice of layout is persisted and restored for the current workspace
  • you can have multiple windows open with different layout choice
• the layout is reflected by the split-icon in the editor header and quick open
• all of the following features still work in both layouts
  • closing groups and opening new editor groups
  • resizing using the sashes
  • DND of editor groups
  • DND of editors by dragging tabs (only when tabs are enabled)
  • DND of editors from outside (e.g. explorer, native files explorer)
  • editors "snap" to minimized when sized small enough and you can jump through the minimized editors making the currently active one maximized
  • you can still use the Panel properly when horizontal layout is enabled
  • all works when tabs are enabled or disabled
• try to break the layout
  • make sidebar large enough that size for editors gets small and start to split editors and change layout
  • same for the panel

We introduced a new setting workbench.editor.defaultSideBySideLayout (we changed this to workbench.editor.defaultEditorGroupLayout for consistency with other commands and options in later builds, please be aware) that allows to change the default layout that should be used for new workspaces.

• Verify changing this setting picks up the layout when opening workspaces for the first time
• Verify this setting is also picked up when opening an empty workspace