18 files declare their use of MenuTreeParameters in Drupal 9

AdminTest.php in core/modules/system/tests/src/Functional/System/AdminTest.php

DisplayPageTest.php in core/modules/views/tests/src/Kernel/Plugin/DisplayPageTest.php

DisplayPathTest.php in core/modules/views_ui/tests/src/Functional/DisplayPathTest.php

MenuForm.php in core/modules/menu_ui/src/MenuForm.php

MenuLinkContentCacheabilityBubblingTest.php in core/modules/menu_link_content/tests/src/Kernel/MenuLinkContentCacheabilityBubblingTest.php

MenuLinkContentDeriverTest.php in core/modules/menu_link_content/tests/src/Kernel/MenuLinkContentDeriverTest.php

MenuLinkDefaultIntegrationTest.php in core/tests/Drupal/KernelTests/Core/Menu/MenuLinkDefaultIntegrationTest.php

MenuLinksTest.php in core/modules/menu_link_content/tests/src/Kernel/MenuLinksTest.php

MenuLinkTreeTest.php in core/tests/Drupal/KernelTests/Core/Menu/MenuLinkTreeTest.php

MenuTreeParametersTest.php in core/tests/Drupal/Tests/Core/Menu/MenuTreeParametersTest.php

MenuTreeStorageTest.php in core/tests/Drupal/KernelTests/Core/Menu/MenuTreeStorageTest.php

MigrateMenuLinkTest.php in core/modules/menu_link_content/tests/src/Kernel/Migrate/d7/MigrateMenuLinkTest.php

PathAliasMenuLinkContentTest.php in core/modules/menu_link_content/tests/src/Kernel/PathAliasMenuLinkContentTest.php

system.module in core/modules/system/system.module

Configuration system that lets administrators modify the workings of the site.

SystemController.php in core/modules/system/src/Controller/SystemController.php

SystemManager.php in core/modules/system/src/SystemManager.php

SystemMenuBlock.php in core/modules/system/src/Plugin/Block/SystemMenuBlock.php

ToolbarController.php in core/modules/toolbar/src/Controller/ToolbarController.php