Allow OSCAL metadata to be edited through the trestle author commands

[jpower432]

Issue description / feature objectives

The objective would be to add a separate file for managing OSCAL metadata that can be used in conjunction with the control markdown.

Caveats / Assumptions

• The file to be edited would be YAML
• The information would be available in the control markdown as read-only (directly or via link)

Completion Criteria

• Initially support populating roles, parties, and responsible-parties

[jpower432]

cc @vikas-agarwal76 @degenaro

[jpower432]

Related to #1538

[github-actions]

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