Allow link templates for wizards

Here is a patch that allows this. As an example from Page Manager of how you would update your route to make use of this:

 entity.page.edit_form:
-  path: '/admin/structure/page_manager/manage/{machine_name}/{step}'
+  path: '/admin/structure/page_manager/manage/{page}/{step}'
   defaults:
     _entity_wizard: 'page.edit'
     _title_callback: '\Drupal\page_manager_ui\Controller\PageManagerController::editPageTitle'
     tempstore_id: page_manager.page
-    page: '{machine_name}'
+    machine_name: page
+    step: general
   options:
     parameters:
+      page:
+        type: entity:page
+      machine_name:
+        type: id_from_entity
   requirements:
     _permission: 'administer pages'

Specifically:

• You can now use {entity_type} in your path, meaning the link template will be able to provide the correct page.
• machin_name now is set to the name of the parameter containing the entity.
• A default for step must be provided for the link template to work, but as link templates only make sense when there is a default, that's fine.
• The machine_name uses the newly provided id_from_entity type. This will pull the id from {page}, whether it's a string (id) or an EntityInterface (loaded entity). You have to define page's upcasting manually as it doesn't automatically merge it in from what I can see.

The following link template is now supported:
$entity_types['page']->setLinkTemplate('edit-form', '/admin/structure/page_manager/manage/{machine_name}/{step}')

As per conversation with @dsnopek on IRC meetup, tests should include making sure we can use access such as _entity_access: page.edit.

The test only patch is a test that checks link templates and demonstrates that they are currently broken.

The full patch contains the code that allows a fix, but also updates ctools_wizard_test module to make use of it and also \Drupal\ctools\Wizard\EntityFormWizardBase to automatically add the entity_type_id to the previous/next parameters.

As per @dsnopek's suggestion, the updates to the test module include switching over to using _entity_access rather than a simple permission check, so it also proves that now works.

Marking back to needs review. The failing tests are also failing in the branch and are unrelated. The WizardRouteTest fails on the current code and correctly passes with the patch!

After a conversation with @EclipseGc, we've decided this is not a blocker for #2550879: Use CTools Wizard API to add/edit Pages (and move plugin UI using PluginWizardInterface). However, we still feel it has real benefit and when this is in will update the wizard in a follow up.