Issue #2145083 by TR, longwave, dawehner: Fix some grammatical badness mostly in Views tests and comments

Revert "Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system."

This reverts commit fc04601c.

Issue #1954892 by dawehner, tim.plunkett, David_Rothstein, effulgentsia: Replace 'theme callback' and hook_custom_theme() with a clean theme negotiation system.

Issue #1959338 by superspring, urwen, tim.plunkett, damiankloip: Reroll: Remove PHP4-style references for objects.

Issue #2084463 by dawehner, pwolanin, David_Rothstein, tim.plunkett, Xano: Convert contextual links to a plugin system similar to local tasks/actions.

Issue #2119881 by damiankloip, dawehner | joachim: Fixed views BulkFormBase shows 'Apply' button twice.

Issue #2113441 by damiankloip: Move remaining views.module helper functions to Drupal\views\Views class.

Issue #2049207 by dlu, blakehall, janstoeckler, ramlev, Moderate | Cottser: Replace .tpl.php with .html.twig in documentation.

Issue #2100329 by cosmicdreams: Use \Drupal instead of Drupal to make IDEs and static code analyse tools happy.

Issue #1751194 by Cottser, mikl, effulgentsia, benjifisher: Introduce hook_theme_suggestions_HOOK() and hook_theme_suggestions_HOOK_alter().

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

Issue #1979038 by dawehner, effulgentsia, tstoeckler: Convert views_ajax_autocomplete_taxonomy() to a Controller.

Issue #2070609 by damiankloip, tstoeckler: Remove obsolete 'module' keys from Views plugin annotations.

Issue #1912604 by joelpittet, mondrake, damiankloip, gollyg, Cottser: Convert theme_views_mini_pager() to twig.

Issue #1911492 by jibran, Manuel Garcia, derhasi, damiankloip, pcambra, dawehner, tstoeckler: Fixed Views try to find Custom StylePlugin template in core/modules/views/templates.

Issue #1911492 by jibran, Manuel Garcia, derhasi, pcambra, dawehner, damiankloip, tstoeckler: Fixed Views try to find Custom StylePlugin template in core/modules/views/templates.

Issue #1847002 by tim.plunkett, effulgentsia, msonnabaum: Move entity type classes from Drupal$provider\Plugin\Core\Entity to Drupal$provider\Entity.

Issue #1911492 by jibran, Manuel Garcia, derhasi, pcambra, dawehner, damiankloip: Fixed Views try to find Custom StylePlugin template in core/modules/views/templates.

Issue #1912600 by joelpittet, bzitzow, dawehner: Remove theme_views_form_views_form() in favour of a prerender callback.

Issue #1933426 follow-up by dawehner: Fixed documentation around drupal_add_js -> drupal_add_library change.

Issue #2022897 by dawehner, sdboyer, tim.plunkett: Shift responsibility for creating unique config id/machine name off of (views) block plugins and onto BlockFormController.

Issue #2050883 by Cottser, tstoeckler, dawehner: Fix references to obsolete functions in code comments in views module

Issue #1812048 by mikeker, Pancho, dawehner, tim.plunkett: Build the exposed form using form API functions.

Issue #2032031 by damiankloip: Deprecate use of views_get_view() function in favour of Views::getView() method.

Issue #1754246 by webflo, swentel, penyaskito, andypost, alexpott, YesCT, dagmar: Languages should be configuration entities.