[fix][sec] Upgrade OpenSearch to 2.19.4 to remediate CVE-2025-9624

[guptas6est]

Fixes #xyz

Main Issue: #xyz

PIP: #xyz

Motivation

The OpenSearch dependency used by the Elasticsearch IO connector pulls in
org.opensearch:opensearch-common transitively via the OpenSearch REST High Level Client.

Versions prior to 2.19.4 are affected by CVE-2025-9624, which allows a denial-of-service
attack via specially crafted query_string inputs.

Upgrading to OpenSearch 2.19.4 remediates this vulnerability while remaining within
the OpenSearch 2.x line to avoid a breaking major upgrade.

Modifications

• Upgraded opensearch.version from 2.16.0 to 2.19.4 in
  pulsar-io/elastic-search/pom.xml.

No functional or behavioral changes are introduced; this is a dependency-only update.

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository: Nordix#17