Network: support for [RoutingPolicyRule] and its most common parameters

[am-beta]

I hope the naming of variables I chose is consistant with the naming chosen so far.

[kpfleming]

It is fine! Generally Ansible uses snake_case and systemd uses CamelCase so that's what I've been doing to translate between them.

[kpfleming]

You'll also need to add an entry in workflow-support/templates/network-vars.yml.j2 since this adds a new block of arguments.

Also, please add an entry in the Unreleased section of CHANGELOG.md and I'll finalize/merge the PR.