Add a new counter metric measuring failed Pods evictions in `vpa-updater`

[vitanovs]

Which component are you using?:

/area vertical-pod-autoscaler

Is your feature request designed to solve a problem? If so describe the problem this feature should solve.:

Similar to the in-place resource updates metrics that include a counter measuring the total number failed attempts

autoscaler/vertical-pod-autoscaler/pkg/utils/metrics/updater/updater.go

Lines 119 to 124 in 0ec850d

	failedInPlaceUpdateAttempts = prometheus.NewCounterVec(
	prometheus.CounterOpts{
	Namespace: metricsNamespace,
	Name: "failed_in_place_update_attempts_total",
	Help: "Number of failed attempts to update Pods in-place.",
	}, []string{"vpa_size_log2", "reason"},

)

the vpa-updater should also measure the total number of failed Pods evictions attempts.

Describe the solution you'd like.:

Add a new counter metric, failed_eviction_attempts_total, that gets increased at

autoscaler/vertical-pod-autoscaler/pkg/updater/logic/updater.go

Lines 302 to 305 in 0ec850d

	evictErr := evictionLimiter.Evict(pod, vpa, u.eventRecorder)
	if evictErr != nil {
	klog.V(0).InfoS("Eviction failed", "error", evictErr, "pod", klog.KObj(pod))
	} else {

via utility function from the updater package, identical to the in-place updates approach

autoscaler/vertical-pod-autoscaler/pkg/utils/metrics/updater/updater.go

Lines 207 to 211 in 0ec850d

	// RecordFailedInPlaceUpdate increases the counter of failed in-place update attempts by given VPA size and reason
	func RecordFailedInPlaceUpdate(vpaSize int, reason string) {
	log2 := metrics.GetVpaSizeLog2(vpaSize)
	failedInPlaceUpdateAttempts.WithLabelValues(strconv.Itoa(log2), reason).Inc()
	}

Describe any alternative solutions you've considered.:

N/A

Additional context.:

The currently available Pods eviction metrics

• evictable_pods_total gauge: measures the current number of Pods to be evicted
• evicted_pods_total counter: measures the total number of Pods that have been successfully evicted by the vpa-updater

are not sufficient to measure a success rate of the eviction operations. With the additional failed_eviction_attempts_total counter, we'll be able to measure both outcomes and perform a

evicted_pods_total / (evicted_pods_total + failed_eviction_attempts_total)

to instrument an observability dashboard.

[vitanovs]

/assign