Allow installing system requirements from custom repos

[AlanCoding]

Followup from https://github.com/oVirt/ovirt-ansible-collection/pull/197

https://github.com/oVirt/ovirt-ansible-collection/pull/197#discussion_r545429088

We have the SDK RPM in our repo oVirt repo [1] and we even prefer it from the PyPI installation. The PyPI is just a feature that is not officially supported by us.

This is not supported, we support installing from EPEL, but we don't have a solution that can scale to source from other repos.

To clarify use case: Collections sometimes want to install RPMs from a custom repo. We have a bindep profile to support EPEL, but we don't have a way for a collection to use a custom bindep profile to mark a requirement to be installed from a custom repo.

[matburt]

This is going to be required for releasing.

[AlanCoding]

We are using a stop-gap solution for several repos already. It's just that oVirt is the one that proves the general point because its repo is so specific to the project.

See where we install some repos in the python-base image:

https://github.com/ansible/python-base-image/blob/2af877dde32d861f57e5432f06f62767245807de/Containerfile#L30-L33

Packages are installed using such a repo in the python-builder image:

https://github.com/ansible/python-builder-image/blob/7324f237ecf0b2852f35c1ac59fdfd4ee1f63dee/scripts/install-from-bindep#L31