[RELEASE] Release version 1.2.0

[github-actions]

Release OpenSearch and OpenSearch Dashboards 1.2.0

I noticed that a manifest was automatically created in manifests/1.2.0. Please follow the following checklist to make a release.

Preparation

• Assign this issue to a release owner.
• Document any new quality requirements or changes.
• Declare a pencils down date for new features to be merged.
• Finalize scope and feature set and update the Public Roadmap.
• Create a version label in each component repo.
• Create a release issue in every component repo that links back to this issue.
• Ensure that all release issues created above are assigned to an owner in the component team.

CI/CD

• Create Jenkins workflows that run daily snapshot builds for OpenSearch and OpenSearch Dashboards.
• Increment each component version to 1.2.0 and ensure working CI in component repositories.
• Make pull requests to add each component to manifests/1.2.0/opensearch-1.2.0.yml and manifests/1.2.0/opensearch-dashboards-1.2.0.yml with the corresponding checks.

Release

• Declare a release candidate build, and publish all test results.
• Verify all issued labeled v1.2.0 in all projects have been resolved.
• Complete documentation for this release.
• Author and publish a blog post for this release.
• Gather, review and publish release notes.
• Publish this release on opensearch.org.

Post Release

• Create release tags for each component.
• Update this template with any new or missed steps.
• Conduct a postmortem, and publish its results.