Create and delete machines via controller

[mhmxs]

I open this PR for transparency. I'm still testing, but i think it is ready to discuss :).

This change doing reconciliation loop for Linode Machines. Only create and delete has been implemented. You can find some buxfixes and code cleanups too, i tried to push the scope as low as possible.

Fixes: #25
Fixes: #11

[mhmxs]

@luthermonson @zliang-akamai I'm a bit afraid of re-queuing every instance we wait for, maybe it makes sense to retry only X times and dropping the event instead of filling workqueue and waste reconciliation threads WDYT?:

if lastKnownState != linodego.InstanceRunning {
			logger.Info("Instance is not ready, wait for running...", "state", lastKnownState)

			res = ctrl.Result{RequeueAfter: reconciler.DefaultMachineControllerWaitForRunningDelay}
		}

[luthermonson]

@luthermonson @zliang-akamai I'm a bit afraid of re-queuing every instance we wait for, maybe it makes sense to retry only X times and dropping the event instead of filling workqueue and waste reconciliation threads WDYT?:

if lastKnownState != linodego.InstanceRunning {
			logger.Info("Instance is not ready, wait for running...", "state", lastKnownState)

			res = ctrl.Result{RequeueAfter: reconciler.DefaultMachineControllerWaitForRunningDelay}
		}

want to extend the back off as it gets older? if these dont end up running we could be in a way worse case for the data center so eventually stopping at 10 or 15min might be plent?

[mhmxs]

@luthermonson It is ready to merge. I couldn't test the change, because of the missing other parts of the project, but verified the behavior based on other well known provider.

[avestuk]

LGTM as is. Comments are nits/prompts for futher discussion we can have after merge if that's desirable.

[avestuk]

What do you think about using the slices package for this?

		if !slices.ContainsFunc(linodeMachine.OwnerReferences, func(or metav1.OwnerReference) bool {
			return or.UID == machine.UID
		}) {
			log.Info("Failed to find the referenced owner machine, skipping reconciliation", "references", linodeMachine.OwnerReferences, "machine", machine.ObjectMeta)
		}
			return ctrl.Result{}, nil

[mhmxs]

@avestuk in my personal opinion is slices package breaks one of the principles of Golang: simplicity. I would be the last who suggest adopting it :D But of course the question is what we think about his teamwise.

[avestuk]

What do you think about breaking the delete/update/create parts of this function out into their own functions? I don't mind if we do it later in another PR (I'm happy to take a crack at it for instance) but I think the function would be more easily understood if we did so.

[luthermonson]

good to see some progress! well done @mhmxs and thanks for the help @avestuk