Add github workflow to build and attach RPMs on release

[op-ct]

At the moment simp-core does not use its own GitHub actions.

In order to have GitHub build & attach RPMs to a new release, it's currently necessary to:

1. Create the GitHub release and
2. Run the release_rpms.yml workflow from another repo, pointing to simp-core and the target release. This
3. This must be done for each target OS

Example:

• (centos8) https://github.com/simp/pupmod-simp-mockup/runs/6275555437
• (centos7) https://github.com/simp/pupmod-simp-mockup/runs/6275632005

[op-ct]

This is still a legitimate issue, but it is coupled with the fact that simp-core also lacks a tag_deploy.yml workflow that would contain the matrix of target OSes to each trigger the release_rpms.yml workflow.

This raises the legitimate question of "what should that look like, given simp-core's rather specialized remit?"

Among other things, simp-core contains the assets needed to build:

• The simp-simp_core puppet module
• The simp RPM
• The simp-build and simp-beaker containers
• The DVD ISO for each target OS flavor + version

So tag_deploy.yml might trigger a lot more than just the simp RPM builds.