Make local overlays local to surface and remove insane z-indexes

ve.ui.Surface.js
* Make local overlay a child of ve-ui-surface and a sibling to
  ve-ce-surface elements.
** This keeps local overlays relative to their surface and eliminates the
   need for insane z-indexes.

ve.ui.PopupWidget.js
* PopupWidget boundaries are now relative to ve-ce-surface and no longer
  protrude out

ve.ce.Node.css, ve.ui.Window.css
* Removal or replacement of insane z-indexes.

ve.ce.FocusableNode.js, ve.ce.ProtectedNode.js, ve.ce.ResizableNode.js,
ve.ui.Context.js
* Translate offsets from local overlay

ve.init.mw.ViewPageTarget-monobook.css,
ve.init.mw.ViewPageTarget-vector.css
* Skin specific z-indexes for global overlay

ve.init.mw.ViewPageTarget.js
* Applied direction specific mw class to ce.Surface vs ui.Surface to
  prevent mw content styles from being applied to ui elements.

ve.ui.Dialog.css
* Adjustments to surface inside of dialog so that relative offsets for
  local overlays can be properly calculated.

ve.ui.Surface.css
* Explicitly force .ve-ui-surface to be relative so that it's children can
  be relatively positioned.

ve.ui.Widget.css
* Removal of unnecessary font-size properties now that local overlay is
  sibling of surface.

ve.js
* Added get relative position helper method to translate position offsets
  from target parent

Bug: 50241
Change-Id: Ibadce404a2286bc5dcec48f0d9da89004dbbd867
Merge "Make local overlays local to surface and remove insane z-indexes"