Refactor: package dom0-specific files instead of inlining them in Salt; separate dom0 files and scripts

[rocodes]

Status

Work in progress - dnm

Description of Changes

Towards #274
Towards #837 (also prereq for moving files out of /srv/salt/ into their own subdirectory)

Prereq: #990

Changes proposed in this pull request:

• Split files (jinja templates, repo files etc) out from sls and top files
• Move dom0 scripts to dom0-scripts directory
• Avoid inline block append/remove to files via Salt states; instead, include those files in the dom0 rpm .spec, so they are managed by the rpm installation (easier to reason about versioning etc)

Testing

TK - not ready for testing yet

• CI green
• Successful provisioning with both prod key and test key

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

[rocodes]

(Closing in favour of new PRs)