Provide a utility funcition in ve.init.mw.LinkCache to do this.
Also use this in ve.ce.MWTransclusionNode/ve.ui.MWPreviewElement, and
introduce to ve.ce.MWExtenionNode
Bug: T73900
Bug: T153535
Change-Id: Ieb9a0274b8c5ae1932c431546f09d18000fa6dd9
This fixes some rendering issues, and also increases the font
size of reference contexts from 12.8px (interface) to 14px (content).
Bug: T119430
Change-Id: Ib1bae8cd4cfe86903d78406a33db78e1489fde86