Include puma logs alongside rails logs in GDK

What does this MR do?

This change makes puma emit its logs to the same stream as rails does, when using the GDK.

This means that if Puma logs any errors, developers will notice them and be able to react.

Additionally, PumaWorkerKiller logs are emitted in the stream, which may help developers realised that their local changes have memory leaks.

cc @ayufan @jacobvosmaer-gitlab

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team