Multiarch test compatibility

[nestoracunablanco]

Currently, the tests assume that all nodes share the same architecture. This is not an issue at the moment, as the functional tests are conducted using a single-architecture cluster (via kubevirtci). However, this approach does not scale to a multi-architecture cluster, as we cannot guarantee the architecture of the node on which KubeVirt will execute the virtual machine.

While there are several possible approaches, implementing a node selector based on architecture appears to be a viable option.