Issue #2348679 by znerol, Wim Leers: Move the remaining procedural page cache code to the page cache stack middleware

Issue #2392787 by beejeebus, dawehner, alexpott: Move include statements from DrupalKernel::boot() into DrupalKernel::preHandle()

Issue #2328111 by dawehner, martin107, neclimdul: Replace most instances of the DRUPAL_ROOT constant with the app.root container parameter.

Issue #2303673 by dawehner, damiankloip, effulgentsia, Fabianx: Implement stackphp; cleanup handlePageCache() and preHandle()

Issue #2016629 by larowlan, neclimdul, sun, alexpott, jibran, ParisLiakos, donquixote, effulgentsia, msonnabaum: Refactor bootstrap to better utilize the kernel.

Revert "Issue #2016629 by larowlan, neclimdul, sun, alexpott, jibran, ParisLiakos, donquixote, effulgentsia, msonnabaum: Refactor bootstrap to better utilize the kernel."

This reverts commit cda051c4.

Issue #2016629 by larowlan, neclimdul, sun, alexpott, jibran, ParisLiakos, donquixote, effulgentsia, msonnabaum: Refactor bootstrap to better utilize the kernel.

This reverts commit ecf2fa72.

This reverts commit c5c075df.

Issue #2004282 by dawehner, smiletrl, amateescu, tim.plunkett: Injected dependencies and serialization hell .

Issue #1988508 by katbailey: Stop pretending we support Symfony bundles when we really just have service providers.

Issue #1849700 by katbailey, effulgentsia: Fixed DrupalKernel's container.modules param should contain module filenames, not full namespace paths.

Issue #1708692 by xjm, effulgentsia, tim.plunkett, fubhy, Berdir, chx: Fixed Bundle services aren't available in the request that enables the module.