Add support for remote agents with SSM

[jramosf]

This Pull Request adds support to launch remote agents using SSM instead of SSH. This removes the need to periodically rotate SSH keys and completely removes need to open SSH ports.

I have read the contributing guidelines and this is my first Pull Request in this project.

Thank you for your time reviewing this.

Testing done

• Tested within own environment as well as fresh Jenkins running in container, using the latest LTS at the time of opening this Pull Request: https://www.jenkins.io/changelog-stable/#v2.541.2
• Container image used: LTS from upstream: https://hub.docker.com/layers/jenkins/jenkins/2.541.2-lts/

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests that demonstrate the feature works or the issue is fixed