Quickfix for Transclusion icon in RTL wikis

Added GUI-level and Page-level "getDir()" methods to get the direction
of the GUI and Page respectively in the ve.ui.Surface and ve.ce.Surface
respectively.

The correction to the direction-test condition in ve.ui.Context reflects
the new method of getting these directions, and fixes the problem with
the transclusion icon. The icon position depends on the wiki/page-level
directionality, regardless of the GUI-level direction.

Bug: 51819
Change-Id: I36cef115017542c461e6d757f1c8bfda92074607
Merge "Quickfix for Transclusion icon in RTL wikis"