[catalog] Make unprocessed entities visible

Create an API route to fetch failed and pending entities, as well as a frontend plugin to view them.

Added a broken entity to the sample data.

Signed-off-by: Rickard Dybeck <dybeck@spotify.com>

packages/app/package.json

@@ -26,6 +26,7 @@
     "@backstage/plugin-catalog-graph": "workspace:^",
     "@backstage/plugin-catalog-import": "workspace:^",
     "@backstage/plugin-catalog-react": "workspace:^",
+    "@backstage/plugin-catalog-unprocessed-entities": "workspace:^",
     "@backstage/plugin-circleci": "workspace:^",
     "@backstage/plugin-cloudbuild": "workspace:^",
     "@backstage/plugin-code-coverage": "workspace:^",