chore: Bump OpenSearch version 3.4.0

[siegfriedweber]

Description

• OpenSearch 3.4.0 added to supported-versions.adoc
• Version 3.4.0 of OpenSearch and OpenSearch Dashboards added to test-definitions.yaml
• All references to version 3.1.0 substituted with 3.4.0
• All links tested, especially that the line numbers did not change
• All integration tests successfully executed:

--- PASS: kuttl (1875.93s)
    --- PASS: kuttl/harness (0.00s)
        --- PASS: kuttl/harness/smoke_opensearch-3.1.0_opensearch_home-_stackable_opensearch_server-use-tls-false (141.75s)
        --- PASS: kuttl/harness/backup-restore_opensearch-3.4.0_s3-use-tls-true_release-0.0.0-dev (395.11s)
        --- PASS: kuttl/harness/metrics_opensearch-3.1.0 (287.07s)
        --- PASS: kuttl/harness/logging_opensearch-3.4.0 (83.12s)
        --- PASS: kuttl/harness/logging_opensearch-3.1.0 (75.19s)
        --- PASS: kuttl/harness/metrics_opensearch-3.4.0 (120.74s)
        --- PASS: kuttl/harness/backup-restore_opensearch-3.1.0_s3-use-tls-true_release-0.0.0-dev (250.51s)
        --- PASS: kuttl/harness/opensearch-dashboards_opensearch-3.1.0_opensearch_home-_stackable_opensearch_server-use-tls-true_release-0.0.0-dev (401.00s)
        --- PASS: kuttl/harness/opensearch-dashboards_opensearch-3.4.0_opensearch_home-_stackable_opensearch_server-use-tls-true_release-0.0.0-dev (422.36s)
        --- PASS: kuttl/harness/opensearch-dashboards_opensearch-3.4.0_opensearch_home-_stackable_opensearch_server-use-tls-false_release-0.0.0-dev (386.93s)
        --- PASS: kuttl/harness/smoke_opensearch-3.4.0_opensearch_home-_stackable_opensearch_server-use-tls-true (119.90s)
        --- PASS: kuttl/harness/external-access_opensearch-3.1.0_opensearch_home-_stackable_opensearch (62.76s)
        --- PASS: kuttl/harness/external-access_opensearch-3.4.0_opensearch_home-_stackable_opensearch (70.39s)
        --- PASS: kuttl/harness/ldap_opensearch-3.4.0_opensearch_home-_stackable_opensearch (92.11s)
        --- PASS: kuttl/harness/opensearch-dashboards_opensearch-3.1.0_opensearch_home-_stackable_opensearch_server-use-tls-false_release-0.0.0-dev (403.20s)
        --- PASS: kuttl/harness/ldap_opensearch-3.1.0_opensearch_home-_stackable_opensearch (90.04s)
        --- PASS: kuttl/harness/smoke_opensearch-3.4.0_opensearch_home-_stackable_opensearch_server-use-tls-false (163.46s)
        --- PASS: kuttl/harness/smoke_opensearch-3.1.0_opensearch_home-_stackable_opensearch_server-use-tls-true (168.88s)

• All Vector unit tests successfully executed:

Running tests
test Test opensearch_server log entry without stacktrace ... passed
test Test opensearch_server log entry with stacktrace ... passed
2026-01-27T16:39:50.531714Z  WARN transform{component_kind="transform" component_id=processed_files_opensearch_server component_type=remap}: vrl::stdlib::log::implementation: JSON not parsable: function call error for "parse_json" at (110:133): unable to parse json: EOF while parsing an object at line 2 column 0 internal_log_rate_secs=1 vrl_position=224
test Test opensearch_server log entry with unparsable message ... passed
2026-01-27T16:39:50.532923Z  WARN transform{component_kind="transform" component_id=processed_files_opensearch_server component_type=remap}: vrl::stdlib::log::implementation: Internal log [JSON not parsable: function call error for "parse_json" at (110:133): unable to parse json: EOF while parsing an object at line 2 column 0] is being suppressed to avoid flooding.
test Test opensearch_server log entry without a JSON object in the message field ... passed
test Test opensearch_server log entry with unparsable timestamp ... passed
test Test opensearch_server log entry without timestamp ... passed
test Test opensearch_server log entry without logger ... passed
test Test opensearch_server log entry without level ... passed
test Test opensearch_server log entry with unknown level ... passed
test Test opensearch_server log entry without message ... passed
test Test Vector internal logs ... passed
test Test Vector internal log level filtering - TRACE/DEBUG ... passed
test Test Vector internal log level filtering - INFO ... passed
test Test Vector internal log level filtering - WARN ... passed
test Test Vector internal log level filtering - ERROR ... passed

(The warnings are expected.)

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

• Changes are OpenShift compatible
• Helm chart can be installed and deployed operator works
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible
• Links to generated (nightly) docs added:
  https://docs.stackable.tech/home/nightly/opensearch/#_supported_versions

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added
• Links to generated (nightly) docs added
• Release note snippet added
• Add type/deprecation label & add to the deprecation schedule
• Add type/experimental label & add to the experimental features tracker

[dervoeti]

LGTM, only the changelog entry is missing