Standardize field_ui entity route names

fix routes for entity view|form displays

Makes sure that entity has bundle, suppose the scope allows

PS: working to fix routes for fields

Patch is not ready, there's routes for field and field config, also this affects content translation which routes needs some clean-up... see comment in #2281645-81: Make entity annotations use link templates instead of route names
The CT routes are tricky but affected by field_ui so probably better to fit them here too

@dawehner I mostly agree, in my vision routes should be renamed in separate issue under the meta
We need to standardize routes without dependency on link templates.

PS: will back to patch next weekend

I'd still prefer to separate route rename issues from logic changes

re-roll after #2281645: Make entity annotations use link templates instead of route names

@dawehner is add-form template is needed?

+++ b/core/modules/field_ui/field_ui.module
@@ -299,8 +299,9 @@ function field_ui_entity_type_alter(array &$entity_types) {
+  $form_mode->setLinkTemplate('add-form', 'entity.entity_form_mode.add_form');

@@ -308,6 +309,7 @@ function field_ui_entity_type_alter(array &$entity_types) {
+  $view_mode->setLinkTemplate('add-form', 'entity.entity_view_mode.add_form');

the only missing part in last patch, not sure is needed

Once this entities have add forms it makes sense to expose them as templates too

+++ b/core/modules/field_ui/src/EntityDisplayModeListBuilder.php
@@ -119,7 +119,7 @@ public function render() {
       $table['#rows']['_add_new'][] = array(
         'data' => array(
           '#type' => 'link',
-          '#url' => Url::fromRoute($short_type == 'view' ? 'field_ui.entity_view_mode_add_type' : 'field_ui.entity_form_mode_add_type', ['entity_type_id' => $entity_type]),
+          '#url' => Url::fromRoute($short_type == 'view' ? 'entity.entity_view_mode.add_form' : 'entity.entity_form_mode.add_form', ['entity_type_id' => $entity_type]),

This is just a rename

needs feedback