Export resource reconciliation metrics in Prometheus format

[stefanprodan]

Instrument the toolkit controllers to export reconciliation metrics for each API type:

# HELP gotk_reconcile_condition The current condition status of a GitOps Toolkit resource reconciliation.
# TYPE gotk_reconcile_condition gauge
gotk_reconcile_condition{kind="Kustomization",name="podinfo",namespace="gotk-system",status="Deleted",type="Ready"} 0
gotk_reconcile_condition{kind="Kustomization",name="podinfo",namespace="gotk-system",status="False",type="Ready"} 0
gotk_reconcile_condition{kind="Kustomization",name="podinfo",namespace="gotk-system",status="True",type="Ready"} 1
gotk_reconcile_condition{kind="Kustomization",name="podinfo",namespace="gotk-system",status="Unknown",type="Ready"} 0

# HELP gotk_reconcile_duration The duration in seconds of a GitOps Toolkit resource reconciliation.
# TYPE gotk_reconcile_duration histogram
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="1e-08"} 0
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="1e-07"} 0
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="1e-06"} 0
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="9.999999999999999e-06"} 0
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="9.999999999999999e-05"} 0
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="0.001"} 0
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="0.01"} 0
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="0.1"} 0
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="1"} 1
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="10"} 2
gotk_reconcile_duration_bucket{kind="Kustomization",name="podinfo",namespace="gotk-system",le="+Inf"} 3
gotk_reconcile_duration_sum{kind="Kustomization",name="podinfo",namespace="gotk-system"} 36.929779548000006
gotk_reconcile_duration_count{kind="Kustomization",name="podinfo",namespace="gotk-system"} 3

Components:

• source-controller
• kustomize-controller
• helm-controller
• notification-controller

Ref: #122 #170