Add pipeline-scheduler pipeline in catalog.info (#39254)

As a follow up to PR#39206 and PR#39171, this commit adds a new generic
scheduling pipeline in catalog-info that serves as a central point
for scheduling any other pipeline.

Unfortunately, it's not possible to specify a custom agent (k8s image)
yet at the catalog-info level[^1], therefore we still need a small
static pipeline -- empty for now -- that uploads the needed steps.

[^1]: https://github.com/elastic/ci/blob/71e83d340e3b93ab43fcf16a7a70ac33bdeec6e9/terrazzo/terrazzo/constructs/buildkite/pipelines.py#L787-L842

catalog-info.yaml

@@ -1113,3 +1113,50 @@ spec:
           access_level: BUILD_AND_READ
         everyone:
           access_level: READ_ONLY
+
+---
+# yaml-language-server: $schema=https://gist.githubusercontent.com/elasticmachine/988b80dae436cafea07d9a4a460a011d/raw/rre.schema.json
+apiVersion: backstage.io/v1alpha1
+kind: Resource
+metadata:
+  name: beats-pipeline-scheduler
+  description: 'Scheduled runs of various Beats pipelines per release branch'
+  links:
+    - title: 'Scheduled runs of Beats pipelines per release branch'
+      url: https://buildkite.com/elastic/logstash-pipeline-scheduler
+spec:
+  type: buildkite-pipeline
+  owner: group:ingest-fp
+  system: buildkite
+  implementation:
+    apiVersion: buildkite.elastic.dev/v1
+    kind: Pipeline
+    metadata:
+      name: beats-pipeline-scheduler
+      description: ':alarm_clock: Scheduled runs of various Beats pipelines per release branch'
+    spec:
+      repository: elastic/beats
+      pipeline_file: ".buildkite/pipeline-scheduler.yml"
+      maximum_timeout_in_minutes: 240
+      schedules:
+        Daily Snapshot DRA:
+          branch: main
+          cronline: 30 02 * * *
+          message: Daily trigger of Iron Bank validation Pipeline per branch
+          env:
+            PIPELINES_TO_TRIGGER: 'beats-ironbank-validation'
+      skip_intermediate_builds: true
+      provider_settings:
+        trigger_mode: none
+      env:
+        # TODO enable slack notifications when it's tested
+        ELASTIC_SLACK_NOTIFICATIONS_ENABLED: 'false'
+        SLACK_NOTIFICATIONS_CHANNEL: '#ingest-notifications'
+        SLACK_NOTIFICATIONS_ON_SUCCESS: 'false'
+      teams:
+        ingest-fp:
+          access_level: MANAGE_BUILD_AND_READ
+        release-eng:
+          access_level: BUILD_AND_READ
+        everyone:
+          access_level: READ_ONLY