WIP: Add DesiredStateChanged event filter

[bobh66]

Description of your changes

Added the DesiredStateChanged EventFilter to the controller to avoid unnecessary reconciliations.

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

Executed this code in a development cluster doing multiple deployments.

[bobh66]

Further testing has revealed a possible issue with Objects not getting updated properly. I'm investigating.

[chlunde]

@bobh66 did you find anything here? for example, if an immutable object is attempted changed, provider-kubernetes "spins" very actively trying to reconcile it :( I think this would fix that

  Type     Reason                        Age                      From                                     Message
  ----     ------                        ----                     ----                                     -------
  Normal   CreatedExternalResource       20m                      managed/object.kubernetes.crossplane.io  Successfully requested creation 
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  8m39s                    managed/object.kubernetes.crossplane.io  cannot apply object: cannot patc
  Warning  CannotUpdateExternalResource  3m38s (x849 over 8m39s)  managed/object.kubernetes.crossplane.io  (combined from similar events): 

full event (example):

  Warning  CannotUpdateExternalResource  4m38s (x849 over 9m39s)  managed/object.kubernetes.crossplane.io  (combined from similar events): cannot apply object: cannot patch object: Job.batch "pi-1" is invalid: spec.template: Invalid value: core.PodTemplateSpec{ObjectMeta:v1.ObjectMeta{Name:"", GenerateName:"", Namespace:"", SelfLink:"", UID:"", ResourceVersion:"", Generation:0, CreationTimestamp:time.Date(1, time.January, 1, 0, 0, 0, 0, time.UTC), DeletionTimestamp:<nil>, DeletionGracePeriodSeconds:(*int64)(nil), Labels:map[string]string{"controller-uid":"030305ca-7ab7-4d05-8c7c-e3cb92e7588f", "job-name":"pi-1"}, Annotations:map[string]string(nil), OwnerReferences:[]v1.OwnerReference(nil), Finalizers:[]string(nil), ManagedFields:[]v1.ManagedFieldsEntry(nil)}, Spec:core.PodSpec{Volumes:[]core.Volume(nil), InitContainers:[]core.Container(nil), Containers:[]core.Container{core.Container{Name:"pi", Image:"perl:5.34.0", Command:[]string{"perl", "-Mbignum=bpi", "-wle", "print bpi(1) second2"}, Args:[]string(nil), WorkingDir:"", Ports:[]core.ContainerPort(nil), EnvFrom:[]core.EnvFromSource(nil), Env:[]core.EnvVar(nil), Resources:core.ResourceRequirements{Limits:core.ResourceList(nil), Requests:core.ResourceList(nil), Claims:[]core.ResourceClaim(nil)}, VolumeMounts:[]core.VolumeMount(nil), VolumeDevices:[]core.VolumeDevice(nil), LivenessProbe:(*core.Probe)(nil), ReadinessProbe:(*core.Probe)(nil), StartupProbe:(*core.Probe)(nil), Lifecycle:(*core.Lifecycle)(nil), TerminationMessagePath:"/dev/termination-log", TerminationMessagePolicy:"File", ImagePullPolicy:"IfNotPresent", SecurityContext:(*core.SecurityContext)(nil), Stdin:false, StdinOnce:false, TTY:false}}, EphemeralContainers:[]core.EphemeralContainer(nil), RestartPolicy:"Never", TerminationGracePeriodSeconds:(*int64)(0x4012805d98), ActiveDeadlineSeconds:(*int64)(nil), DNSPolicy:"ClusterFirst", NodeSelector:map[string]string(nil), ServiceAccountName:"", AutomountServiceAccountToken:(*bool)(nil), NodeName:"", SecurityContext:(*core.PodSecurityContext)(0x4017a80750), ImagePullSecrets:[]core.LocalObjectReference(nil), Hostname:"", Subdomain:"", SetHostnameAsFQDN:(*bool)(nil), Affinity:(*core.Affinity)(nil), SchedulerName:"default-scheduler", Tolerations:[]core.Toleration(nil), HostAliases:[]core.HostAlias(nil), PriorityClassName:"", Priority:(*int32)(nil), PreemptionPolicy:(*core.PreemptionPolicy)(nil), DNSConfig:(*core.PodDNSConfig)(nil), ReadinessGates:[]core.PodReadinessGate(nil), RuntimeClassName:(*string)(nil), Overhead:core.ResourceList(nil), EnableServiceLinks:(*bool)(nil), TopologySpreadConstraints:[]core.TopologySpreadConstraint(nil), OS:(*core.PodOS)(nil), SchedulingGates:[]core.PodSchedulingGate(nil), ResourceClaims:[]core.PodResourceClaim(nil)}}: field is immutable

in this case, the randomness is here: ...SecurityContext:(*core.PodSecurityContext)(0x400ae701b0)...

[turkenh]

@bobh66 do you still want to proceed here?