Issue #2061977 by InternetDevels, kim.pepper, ianthomas_uk, herom: Replace user_access() calls with ->hasPermission() in all core modules except user.
Issue #2301493 by alexpott: Fixed Typehint Drupal\file\File is does not exist.
Issue #2286923 by cs_shadow, alayham: Fixed views_ui dropbuttons are not RTL friendly.
Issue #2301599 by Cottser, mparker17: Fixed Regression: Bartik's field--taxonomy-term-reference.html.twig doesn't properly output label attributes.
Issue #2300857 by joshi.rohit100: Remove lock() method from bootstrap.inc as deprecated.
Issue #2299691 by er.pushpinderrana, jhodgdon: Some topics should be removed.
Issue #2300831 by joshi.rohit100: Remove module_exists() as it is deprecated.
Revert "Issue #2061977 by InternetDevels, kim.pepper, ianthomas_uk, herom: Replace user_access() calls with ->hasPermission() in all core modules except user."

Fixing commit credit.

This reverts commit 25afa8100ab9a3786594e8fc791c1d76490c42d0.
Issue #2061977 by InternetDevels, kim.pepper, ianthomas_uk, herom, rhm50, naveenvalecha, andypost,  mandar.harkare, sergeypavlenko, sidharthap, SIz, tkuldeep17: Replace user_access() calls with ->hasPermission() in all core modules except user.
Issue #1856562 by andypost | sun: Convert "Subject" and "Message" into Message base fields.
Issue #2080311 by rhm50, amitgoyal, InternetDevels, Rajesh Ashok, pfrenssen, natemow, areke, chertzog | mrsinguyen: Clean up Drupal\system\Tests\Database\SelectTest.php.
Issue #2301975 by kim.pepper: Move drupal_is_front_page to PathMatcher service.
Issue #2301597 by joshi.rohit100: Remove drupal_prepare_form() as it is deprecated.
Issue #2300891 by joshi.rohit100: Remove format_backtrace() from error.inc as deprecated.
Issue #2300853 by joshi.rohit100: Remove language() method from bootstrap.inc as it is deprecated.
Issue #2301577 by ParisLiakos, joshi.rohit100: Remove drupal_alter() as it is deprecated.
Issue #2301587 by joshi.rohit100: Remove form_state_defaults() as it is deprecated.
Issue #2301601 by joshi.rohit100: Remove drupal_validate_form() as it is deprecated.
Issue #1587270 by klausi, greggles, sun: Forbid execution of PHP files in subfolders by default (except those needed by core).
Issue #2296237 by er.pushpinderrana: Replace check_plain() to Drupal\Component\Utility\String::checkPlain() in file module.