Issue #2512132 by Wim Leers, effulgentsia, Fabianx: Make CSRF links cacheable

core/lib/Drupal/Core/Url.php

core/lib/Drupal/Core/Utility/LinkGenerator.php

core/lib/Drupal/Core/Utility/LinkGeneratorInterface.php

core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php

...lib/Drupal/Core/Utility/UnroutedUrlAssemblerInterface.php

...s/help/tests/modules/help_test/src/SupernovaGenerator.php

...modules/language/src/HttpKernel/PathProcessorLanguage.php

...Plugin/LanguageNegotiation/LanguageNegotiationSession.php

...src/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php

...es/language/tests/src/Unit/LanguageNegotiationUrlTest.php

...ent/src/Tests/MenuLinkContentCacheabilityBubblingTest.php

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

...modules/system/src/Tests/RouteProcessor/RouteNoneTest.php

...s/RouteProcessor/RouteProcessorCurrentIntegrationTest.php

...em/tests/modules/url_alter_test/src/PathProcessorTest.php

...tests/Drupal/Tests/Core/Access/RouteProcessorCsrfTest.php

...rupal/Tests/Core/PathProcessor/PathProcessorAliasTest.php

...l/Tests/Core/RouteProcessor/RouteProcessorManagerTest.php

core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php

core/tests/Drupal/Tests/Core/UrlTest.php