Issue #2209293 by sun, xjm: Remove core compatibility check in ExtensionDiscovery; obsolete with Migrate in core.
Issue #1959660 by larowlan, pfrenssen, xjm, clemens.tolboom, dawehner, RobLoach: Replace xpath() with WebTestBase::cssSelect() by leveraging Symfony CssSelector.
Issue #2236781 by damiankloip, alexpott, xjm: Fixed ViewsData only writes one per-table cache entry per request.