In preparation for moving the languages out of the sidebar (T256023)
and to facilitate experimentation in the Universal Language Selector
extension, we should separate the data from the languages portal
from other portals.
Note the languages portal has traditionally appeared at the bottom
of the sidebar, so this can be done safely in the same way we
introduced data-portals-first
Change-Id: I4be06278ec256cc55aee36c2946339fb49d21b46
Split out the sidebar in advance of significant Latest mode only
changes.
The Less split was made by adding a new Sidebar.less file that imports
the Legacy implementation.
The Mustache split was made by file copying the existing implementation
into a legacy/ subfolder. Both the Legacy and Latest implementations
were then stripped of templates not applicable to their modes.
These changes are aligned with the splits for JavaScript.
Bug: T246419
Change-Id: Ib82769ea16bfc09efe8a088220aab55bdde0d381
jdlrobson
Stephen Niedzielski