Issue #2557467 by alexpott: Deprecate check_url and convert usages to existing UrlHelper methods

core/includes/common.inc

core/includes/install.core.inc

core/includes/install.inc

core/lib/Drupal/Component/Utility/UrlHelper.php

core/modules/aggregator/aggregator.theme.inc

core/modules/comment/comment.tokens.inc

core/modules/comment/src/Tests/CommentTokenReplaceTest.php

core/modules/filter/filter.module

core/modules/search/search.pages.inc

core/modules/system/src/Tests/Common/UrlTest.php

core/modules/system/src/Tests/Common/XssUnitTest.php

core/tests/Drupal/Tests/Component/Utility/UrlHelperTest.php