Update junit-annotate plugin to use container image for faster execution

- Updated junit-annotate plugin from v2.4.1 to v2.7.0
- Replaced GCP provider with container image docker.elastic.co/ci-agent-images/buildkite-junit-annotate:1.0
- Added run-in-docker: false configuration
- This should result in faster execution as requested in the issue

Fixes #108

Co-authored-by: v1v <[email protected]>

Author: Copilot

.buildkite/pipeline.yml

@@ -22,11 +22,12 @@ steps:
   - key: junit
     label: ":junit: Test results"
     agents:
-      provider: "gcp"
-      image: family/core-ubuntu-2204
+      # requires at least "bash", "curl" and "git"
+      image: "docker.elastic.co/ci-agent-images/buildkite-junit-annotate:1.0"
     plugins:
-      - junit-annotate#v2.4.1:
+      - junit-annotate#v2.7.0:
           artifacts: "junit-output/junit-*.xml"
           job-uuid-file-pattern: "junit-(.*).xml"
           fail-build-on-error: true
           failure-format: file
+          run-in-docker: false