JENKINS-73398: Support credential snapshots

[mtughan]

Support taking snapshots of Vault secrets to allow them to be used properly on agents.

Testing done

Have run this locally in combination with jenkinsci/artifactory-artifact-manager-plugin#53 and it works a charm.

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 demonstrates feature works or fixes the issue

[mtughan]

@jenkinsci/hashicorp-vault-plugin-developers, please review when you have a chance.

[mtughan]

@jenkinsci/hashicorp-vault-plugin-developers, any updates here? This PR seems to be languishing.

[mtughan]

Thanks @jetersen!