[exporter/opensearch] Add pipeline option for ingest pipeline support

[robertpaschedag]

Description

Add an optional pipeline configuration parameter to the OpenSearch exporter. When set, the specified ingest pipeline ID is passed to the bulk indexer, causing all documents to be
processed by the pipeline before being indexed in OpenSearch.

Link to tracking issue

Fixes #47227

Testing

Testing was done manually by passing the pipeline option to a running opensearch instance. Passing the name of an ingest pipeline that does not exist, returns a permanent error (as expected). Also, a permanent error is returned, if there is no node in the cluster, that has the ingest node role assigned.

exporters:
  opensearch:
    http:
      endpoint: <endpoint>
      tls:
        ...
    pipeline: otel-ingest-pipeline

Documentation

- `pipeline` (optional): the ID of an [ingest pipeline](https://opensearch.org/docs/latest/ingest-pipelines/) to apply when indexing documents. When set, all documents sent via the bulk API will be processed by the specified pipeline before being indexed. The ingest pipeline must exist in the cluster and there must be a least one node with the `ingest` node role assigned.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: robertpaschedag / name: Robert Paschedag (336d66d, 83f0ea0, 8fb28c1, bfe90f4, d8dc2d1, ea326d0)

[github-actions]

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[paulojmdias]

/workflow-approve

[robertpaschedag]

/rerun