Issue #3425419 by andypost, smustgrave: [11.x] Remove deprecated code from system module

core/includes/bootstrap.inc

core/lib/Drupal/Core/Asset/CssCollectionOptimizer.php

core/lib/Drupal/Core/Asset/JsCollectionOptimizer.php

core/lib/Drupal/Core/Block/BlockPluginTrait.php

core/modules/layout_builder/layout_builder.module

...a/tests/src/FunctionalJavascript/MediaSourceImageTest.php

core/modules/system/config/schema/system.schema.yml

core/modules/system/src/Controller/AdminController.php

core/modules/system/src/Controller/DbUpdateController.php

core/modules/system/src/DateFormatListBuilder.php

core/modules/system/src/EventSubscriber/ConfigCacheTag.php

core/modules/system/src/Form/DateFormatDeleteForm.php

core/modules/system/src/Form/DateFormatEditForm.php

core/modules/system/src/MachineNameController.php

core/modules/system/src/Plugin/ImageToolkit/GDToolkit.php

core/modules/system/system.module

core/modules/system/system.routing.yml

...nitoring_test/database_statement_monitoring_test.info.yml

...e_statement_monitoring_test/src/LoggedStatementsTrait.php

...tabase_statement_monitoring_test/src/mysql/Connection.php