Re-add custom flash service so engines can extend cluster's template (#19963)

* Revert "UI: Remove custom service (#19925)"

This reverts commit b04751d224.

* replace stickyInfo with options info

* revert replacing custom stickyInfo

* change flash message name to be consistent throughout application

* make service imports consistent for k8 engine

* replace stickyInfo with options info

* Revert "change flash message name to be consistent throughout application"

This reverts commit 17de49894de3976ed708fcf15f19f6f1eb1012a5.

* add comment

---------

Co-authored-by: Chelsea Shaw <cshaw@hashicorp.com>

ui/lib/kubernetes/addon/engine.js

@@ -16,7 +16,7 @@ export default class KubernetesEngine extends Engine {
   modulePrefix = modulePrefix;
   Resolver = Resolver;
   dependencies = {
-    services: ['router', 'store', 'secret-mount-path', 'flashMessages'],
+    services: ['router', 'store', 'secret-mount-path', 'flash-messages'],
     externalRoutes: ['secrets'],
   };
 }

ui/lib/kubernetes/package.json

@@ -7,7 +7,6 @@
   "dependencies": {
     "ember-cli-htmlbars": "*",
     "ember-cli-babel": "*",
-    "ember-cli-flash": "*",
     "ember-concurrency": "*",
     "@ember/test-waiters": "*",
     "ember-inflector": "*"