from an approach that loaded the runners only once at the startup
to a method that will be repeated i.e. if the Nomad Event Stream connection interrupts.
that was caused by creating an intermediate environment `fetchedEnvironment` when fetching the environments but not removing it in case that we just copy its configuration to the existing environment.
into the utils including all other retry mechanisms.
With this change we fix that the WatchEventStream goroutine does not stop directly when the context is done (but previously only one second after).
In today's unattended upgrade, we have seen how the prewarming pool size dropped to (near) zero. This was based on lost Nomad allocations. The allocations got rescheduled, but not added again to Poseidon.
The reason for this is a miscommunication between the Event Handling and the Nomad Manager. `removedByPoseidon` was true even if the runner was not removed by the manager, but an idle runner.
as second criteria (next to the maximum number of attempts) for canceling the retrying. This is required as we started with the previous commit to retry the nomad environment recovery. This always fails for unit tests (as they are not connected to an Nomad cluster). Before, we ignored the one error but the retrying leads to unit test timeouts.
Additionally, we now stop retrying to create a runner when the environment got deleted.
