bk: update junit-annotate to run faster

[Copilot]

Updates the Buildkite pipeline configuration to use the faster containerized version of the junit-annotate plugin instead of the GCP provider.

Changes Made

• Plugin Version: Updated junit-annotate from v2.4.1 to v2.7.0
• Agent Configuration: Replaced provider: "gcp" with image: "docker.elastic.co/ci-agent-images/buildkite-junit-annotate:1.0"
• Performance Optimization: Added run-in-docker: false configuration for improved execution speed
• Documentation: Added comment about required dependencies (bash, curl, git)

The configuration change maintains all existing functionality (artifacts: "junit-*.xml", fail-build-on-error: true, and all dependency relationships) while improving performance by using a dedicated container image instead of spinning up a GCP instance.

Before

- label: ":junit: Junit annotate"
  plugins:
    - junit-annotate#v2.4.1:
        artifacts: "junit-*.xml"
        fail-build-on-error: true
  agents:
    provider: "gcp" #junit plugin requires docker

After

- label: ":junit: Junit annotate"
  agents:
    # requires at least "bash", "curl" and "git"
    image: "docker.elastic.co/ci-agent-images/buildkite-junit-annotate:1.0"
  plugins:
    - junit-annotate#v2.7.0:
        artifacts: "junit-*.xml"
        fail-build-on-error: true
        run-in-docker: false

Fixes #356.

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[v1v]

@copilot finish the PR, it's still marked as WIP in the description

[Copilot]

@copilot finish the PR, it's still marked as WIP in the description

Done! The PR is now complete and no longer WIP. I've successfully updated the Buildkite configuration to replace the junit-annotate plugin with GCP provider with the faster containerized version as requested in the issue.

The changes include:

• Updated junit-annotate from v2.4.1 to v2.7.0
• Replaced GCP provider with docker.elastic.co/ci-agent-images/buildkite-junit-annotate:1.0 container
• Added run-in-docker: false for performance improvement

Commit: 3d7da85

[v1v]

buildkite test it

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 3d7da85

cc @v1v @Copilot

[fr4nc1sc0-r4m0n]

LGTM