mw.ViewPageTarget.init: Move conditionals client-side

Load the module always and have the conditionals on the
client-side so that we can change these without running into
problems with the new conditions not being rolled-out quickly
for anonymous users because the load queue is in the HTML
and cached for 30+ days.

This also allows us to fix above problem retroactively in wmf
production by just adding a mw.loader.load for this module
in something like MediaWiki:Common.js or something else that is
already in the cached load queue (temporarily, until the cache
has rolled over).

Removed unreachable code for loading ext.visualEditor.splitTest.

Change-Id: I21114960a88d224747447f2dc83d17d160f5f066
Merge "mw.ViewPageTarget.init: Move conditionals client-side"