Oops. Wrong commit credit.

This reverts commit 6d5899ec.

Revert "Issue #2047633 by dawehner, pwolanin, Xano, amateescu, tim.plunkett: Move definition of menu links to hook_menu_link_defaults(), decouple key name from path, and make 'parent' explicit."

This reverts commit 531fd593.

Issue #2047633 by dawehner, pwolanin, Xano, amateescu, tim.plunkett: Move definition of menu links to hook_menu_link_defaults(), decouple key name from path, and make 'parent' explicit.

Issue #2175765 by alexpott, Gábor Hojtsy: Fix comment in system_theme_default() to not refer to obsolete function

Issue #1987854 by splatio, disasm, kim.pepper, vijaycs85, sidharthap, dawehner: Convert system_themes_page() to a new style controller.

Issue #2109303 by damiankloip, ParisLiakos: Convert CSRF checks in controllers to the routing system.

Issue #2102125 by dawehner, tim.plunkett, neclimdul, pwolanin, YesCT, damiankloip, Tim Bozeman: Big Local Task Conversion.

Issue #2009674 by pplantinga, Samvel, dmitrii: Replace theme() with drupal_render() in system module.

Issue #1199946 by alexpott, fubhy, bojanz, steinmb, chx, catch: Fixed Disabled modules are broken beyond repair so the 'disable' functionality needs to be removed.

Issue #2089635 by tim.plunkett, disasm, larowlan: Convert non-test non-form page callbacks to routes and controllers.

Issue #2080069 by mrsinguyen: Remove Unused local variable $stripe from /core/modules/system/system.admin.inc.

Issue #1987816 by pdrake, disasm, ParisLiakos, pguillard, vijaycs85, dawehner: Convert system_batch_page() to a new style controller.

Issue #1987814 by juampy, tim.plunkett, lliss, kushrohra: Convert system_admin_menu_block_page() to a new style controller.

Issue #1987818 by jlbellido, MattDanger, disasm, vijaycs85: Convert system_date_format_language_overview_page() to a new style controller.

Issue #1987810 by nick_schuch, dawehner, vijaycs85, tim.plunkett: Convert system_admin_config_page() to a new style controller.

Issue #2010086 by helga.chb, somepal, jenlampton, IshaDakota: Replace theme() with drupal_render() in system module for  theme_system_themes_page().

Issue #1668866 by ParisLiakos, aspilicious, tim.plunkett, pdrake, g.oechsler, dawehner, Berdir, corvus_ch, damiankloip, disasm, marcingy, neclimdul: Replace drupal_goto() with RedirectResponse.

Issue #1363112 by mparker17, mgifford, tlattimore, Jacine, dcmouyard, bowersox, ry5n, ahdiaz: Simplify names of 'element-x' helper classes.

Issue #1861702 by echoz, rteijeiro, LewisNyman, mcjim: Add a responsive grid to the Appearance page.

Issue #1987824 by nick_schuch, vijaycs85, ParisLiakos: Convert system_php() to a new style controller.

Issue #1957154 by joates, ayelet_Cr, xjm | Berdir: Replace calls to drupal_container()->get('module_handler()') service with Drupal::moduleHandler().