Issue #2417567 by xjm, effulgentsia, mpdonadio, hussainweb: Rename user-path: scheme to internal:

core/lib/Drupal/Core/Url.php

...es/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php

.../modules/link/src/Plugin/Field/FieldWidget/LinkWidget.php

core/modules/menu_link_content/menu_link_content.module

.../modules/menu_link_content/src/Entity/MenuLinkContent.php

core/modules/menu_link_content/src/Tests/LinksTest.php

...enu_link_content/src/Tests/MenuLinkContentDeriverTest.php

...les/menu_link_content/src/Tests/MenuLinkContentUITest.php

...u_link_content/src/Tests/PathAliasMenuLinkContentTest.php

core/modules/menu_ui/src/Tests/MenuCacheTagsTest.php

core/modules/menu_ui/src/Tests/MenuTest.php

...drupal/config/install/migrate.migration.d6_menu_links.yml

...rate_drupal/src/Plugin/migrate/process/d6/InternalUri.php

...dules/migrate_drupal/src/Tests/d6/MigrateMenuLinkTest.php

core/modules/rdf/src/Tests/Field/LinkFieldRdfaTest.php

...modules/shortcut/src/Controller/ShortcutSetController.php

core/modules/shortcut/src/Tests/ShortcutCacheTagsTest.php

core/modules/shortcut/src/Tests/ShortcutLinksTest.php

core/modules/shortcut/src/Tests/ShortcutTestBase.php

.../modules/shortcut/src/Tests/ShortcutTranslationUITest.php