Issue #2563805 by andriyun, subhojit777, joshi.rohit100, naxolozano: Remove usage and function of test_page_test_page()

Issue #2560641 by alexpott, lauriii, Xano, borisson_, ianthomas_uk, olli: Remove all usages SafeMarkup::checkPlain() from render arrays

Revert "Issue #2560641 by alexpott, lauriii, Xano, borisson_, ianthomas_uk: Remove all usages SafeMarkup::checkPlain() from render arrays"

This reverts commit 31007609.

Issue #2560641 by alexpott, lauriii, Xano, borisson_, ianthomas_uk: Remove all usages SafeMarkup::checkPlain() from render arrays

Issue #2548009 by larowlan, dawehner, bircher: Overridden menu links lose parent, expanded and enabled (are disabled) status on cache clear

Issue #2505989 by alexpott, dawehner, olli: Controllers render caching at the top level and setting a custom page title lose the title on render cache hits

Issue #2301317 by pwolanin, dawehner, Wim Leers, effulgentsia, YesCT, xjm, alexpott: MenuLinkNG part4: Conversion.

Revert "Issue #2301317 by pwolanin, effulgentsia, Wim Leers, dawehner, alexpott: MenuLinkNG part4: Conversion."

This reverts commit fd2db9cd.

Issue #2301317 by pwolanin, effulgentsia, Wim Leers, dawehner, alexpott: MenuLinkNG part4: Conversion.

Issue #2068471 by dawehner, Crell, tim.plunkett, jibran, fubhy, larowlan: Normalize Controller/View-listener behavior with a Page object.

Issue #2095121 by clemens.tolboom, jibran: Ensure every path in routing.yml files has a leading slash.

Issue #2076085 by dawehner, damiankloip, Letharion, pwolanin: Resolve the need for a 'title callback' using the route .

Issue #2051097 by dawehner, Manuel Garcia, tlattimore, neclimdul: Change 'pattern' to 'path' in *.routing.yml files.

Issue #1981368 by tim.plunkett, Crell, webchick: Convert all routes to 'module_name().foo_bar()' naming convention.

Issue #2032535 by dawehner, katbailey, pwolanin, Crell: Resolve 'title/title callback' by adding a _title propery on the route and allow a title be part of the render array.