Support multiple PrivateLoadZone objects

[yorugac]

Feature Description

As of now, k6-operator supports only one PrivateLoadZone at a time, or per installation. We'd like to extend support to multiple PrivateLoadZones.

Suggested Solution (optional)

The reconciler should move out polling logic into a new abstraction, with each PrivateLoadZone having its own goroutine to set up the poller, the factory and to handle the updates from the reconciler async.

The max number of PrivateLoadZones should be regulated by GCk6 and not by k6-operator.

Already existing or connected issues / PRs (optional)

No response

[yorugac]

Note: this work will not impact the load distribution of the test. IOW, even with multiple PLZs in the cluster, we'll support only 100% load or using 1 private load zone per test run.