Enable multihost runs with RPMs from PR

[engelmi]

Please describe what you would like to see

In #878 a workflow was added to run Integration Tests in multihost mode on testing farm. This, however, is currently only possible for the latest RPM in the snapshot repo of copr (https://copr.fedorainfracloud.org/coprs/g/centos-automotive-sig/bluechi-snapshot).

It would be great to enhance this workflow (https://github.com/eclipse-bluechi/bluechi/blob/main/.github/workflows/multihost-tests.yml) to be able to run RPMs also created from a PR.

Please describe your use case

When changes in BlueChi itself are required, it would be great to test those while the PR is still open and there is no need to merge.