Avoid url hack in Url schema plugin

After #2448225: Filter container list for schema URI and origin URI this problem has activated. Because url is parsed from current request there is a problem if we click on "Show content in a new button" from this url http://.../admin/content/collect/11?destination=/admin/content/collect (url is created if we click on 'View' button on container listing page).
In uploaded patch, replaced url parsing with container id from the collect container object, which we can get from current request.

Yeah, that looks ugly. The proposed solution already looks better... But it still looks like a workaround.

We need a test that exactly shows how it is currently broken and fixed after with that destination parameter.

Added tests to assert that generated web page is accessible. Also provided test-only patch.

+++ b/src/Plugin/collect/Schema/FetchUrlSchema.php
@@ -96,8 +96,7 @@ class FetchUrlSchema extends SchemaBase implements SpecializedDisplaySchemaInter
+    $collect_container_id = \Drupal::requestStack()->getCurrentRequest()->get('collect_container')->id();

\Drupal::routeMatch()->getRawParameter('collect_container') should give you the same.

And yeah not pretty. It's still relying on the current route, which will be a problem if this is every called in a different way?

Apparently we are relying on it, shouldn't we pass the entity or $items into this method? Or have a generic $context array, if the container is there, use it, if not, don't display this link?

Added collect container as a second parameter in build() method (SpecializedDisplaySchemaInterface class) so we can always get needed collect container id.

Fixxxed. Thx!