[META] Automate artifact signing with OpensearchSignerClient for linux

[abhinavGupta16]

Is your feature request related to a problem? Please describe

Signing currently is a long painstaking process. It needs to be automated to save time when releasing artifacts. We need a tool to be able to sign all artifacts -

• opensearch
• opensearch-dashboards

Describe the solution you'd like

Use the existing Signer.py class to sign the artifacts and generate ".sig" file along with ".asc" files.

Tasks

• upgrade Signer.py to be able to sign artifacts with .sig in a directory  #1382
• Add support to add signer process to artifacts promotions #1383
• Create Jenkins job to sign and upload standalone artifacts #1385

Acceptance Criteria

• User is able to provide the artifact directory and tool is able to sign all the artifacts in the directory
• User is able to pass the artifact path and the tool is able to sign the artifact

Next Steps

Next steps would include to extend this process over for mac and windows

[peternied]

This workflow supports this scenario https://github.com/opensearch-project/opensearch-build/blob/main/jenkins/sign-artifacts/sign-standalone-artifacts.jenkinsfile