[master] Port Same-Site Cookies to master

apps/files/lib/Controller/ApiController.php

core/js/config.php

lib/base.php

lib/private/AppFramework/Http/Request.php

...ware/Security/Exceptions/StrictCookieMissingException.php

...e/AppFramework/Middleware/Security/SecurityMiddleware.php

lib/private/legacy/eventsource.php

lib/private/legacy/json.php

lib/public/IRequest.php

lib/public/Util.php

tests/lib/AppFramework/Http/RequestTest.php

...pFramework/Middleware/Security/SecurityMiddlewareTest.php