WIP: Configure dom0 rpm repo settings via boostrap rpm package.

[rocodes]

Status

Work in progress, pushing in draft mode to discuss approach
Blocked on release of securedrop-workstation-keyring boostrap rpm (to fpf repos at minimum)

Description of Changes

Refs #945
Description TK
For details on specifying rpm dependencies/requirements/constraints, see https://rpm-software-management.github.io/rpm/manual/boolean_dependencies.html

Changes proposed in this pull request:

Testing

If you made non-trivial code changes, include a test plan and validated it for this PR.

Deployment

Any special considerations for deployment? Consider both:

1. Upgrading existing pilot instances
2. New installs

Checklist

If you have made changes to the provisioning logic

• All tests (make test) pass in dom0

If you have added or removed files

• I have updated MANIFEST.in and rpm-build/SPECS/securedrop-workstation-dom0-config.spec

If documentation is required

• I have opened a PR in the docs repo for these changes, or will do so later
• I would appreciate help with the documentation