Release notes

Fixed the configuration reload process to clean up the pipeline's metric store, so it does not retain references to failed pipelines components.

What does this PR do?

Ensure the pipeline's metrics are cleaned on the shutdown, so failed config reloads does not leak metrics from old pipeline reloads attempts.

Why is it important/What is the impact to the user?

Those stale metrics are consuming memory and are being returned on the stats API, causing confusion and huge payloads.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files (and/or docker env variables)
• I have added tests that prove my fix is effective or that my feature works

Related issues

• Closes: Failed config reloads in Logstash causes resources leaks #16202