If a new feature lands on kubevirt, we would need to wait for stable kubevirt release atm in order to consume it by OVN K8s, because OVN installs only last stable

Allow using nightlies as well
Suggested possible values for the new flag:
Stable = Install last stable (as done now, default)
Nightly = Install last nightly
Specific Nightly version = Install that one, good to be used on CI until there is a new stable
Specific Stable Version

There will be just one flag, that can determine between the last two according the format of the tag (first two are just the string themselves).

We can also add a mechanism that in case Specific Nightly version is used,
it will install that, as long as the last stable is older than that, but it might be overkill.
The advantage of it, is that once used, we won't need to change it once there is a new stable, it will auto pick it.
Anyhow will skip this one unless desired.