[BUG] In OpenSearch pipelines, ${pipelineName} variable does not get replaced in s3 key_path_prefix

Describe the bug

The ${pipelineName} variable does not get replaced in this field:

  sink:
    - opensearch:
        ...
        dlq:
          s3:
            bucket: "our_dlq_bucket"
            key_path_prefix: "${pipelineName}/logs/dlq"

To Reproduce
Steps to reproduce the behavior:
Create a pipeline with a DLQ for the sink and use the ${pipelineName} variable to construct an object key prefix.

Object keys will contain "${pipelineName}" instead of the pipeline name.

Expected behavior
Object key should contain the actual pipeline name

Screenshots
n/a

Environment (please complete the following information):
n/a

Additional context
This is trivial to hard-code the pipeline name in each pipeline definition, but most users will expect this to work like it does for the ingestion path: https://docs.aws.amazon.com/opensearch-service/latest/developerguide/creating-pipeline.html#pipeline-path

No source files or tests are named. Start by locating the DLQ S3 key_path_prefix handling and compare it with the ingestion path referenced in the issue. Confirm that ${pipelineName} resolves to the pipeline name in generated object keys and add coverage for the reproduced configuration.