Add dedicated pipeline for ecs dynamic template tests (#99353)

Related to work done by https://github.com/elastic/elasticsearch/pull/97901

.buildkite/pipelines/ecs-dynamic-template-tests.yml

@@ -0,0 +1,9 @@
+steps:
+  - label: ecs-dynamic-templates-tests
+    command: .ci/scripts/run-gradle.sh -Dbwc.checkout.align=true -Dtests.configure_test_clusters_with_one_processor=true :x-pack:plugin:stack:javaRestTest
+    timeout_in_minutes: 420
+    agents:
+      provider: gcp
+      image: family/elasticsearch-ubuntu-2004
+      diskSizeGb: 350
+      machineType: custom-32-98304

catalog-info.yaml

@@ -269,3 +269,37 @@ spec:
           branch: lucene_snapshot
           cronline: "0 9,12,15,18 * * * America/New_York"
           message: "Runs tests against lucene_snapshot branch several times per day"
+---
+# yaml-language-server: $schema=https://gist.githubusercontent.com/elasticmachine/988b80dae436cafea07d9a4a460a011d/raw/e57ee3bed7a6f73077a3f55a38e76e40ec87a7cf/rre.schema.json
+apiVersion: backstage.io/v1alpha1
+kind: Resource
+metadata:
+  name: buildkite-pipeline-elasticsearch-ecs-dynamic-template-tests
+  description: Runs ECS dynamic template tests against main branch
+  links:
+    - title: Pipeline
+      url: https://buildkite.com/elastic/elasticsearch-ecs-dynamic-template-tests
+spec:
+  type: buildkite-pipeline
+  system: buildkite
+  owner: group:elasticsearch-team
+  implementation:
+    apiVersion: buildkite.elastic.dev/v1
+    kind: Pipeline
+    metadata:
+      description: ":elasticsearch: ECS dynamic template tests against main branch"
+      name: elasticsearch / ecs-dynamic-templates / tests
+    spec:
+      repository: elastic/elasticsearch
+      pipeline_file: .buildkite/pipelines/ecs-dynamic-template-tests.yml
+      provider_settings:
+        trigger_mode: none
+      teams:
+        elasticsearch-team: {}
+        ml-core: {}
+        everyone:
+          access_level: READ_ONLY
+      schedules:
+        Daily:
+          branch: main
+          cronline: "0 12 * * * America/New_York"