prometheus: Add experimental deployment

infrastructure/prometheus/kustomization.yaml

+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+namespace: cert-manager
+resources:
+  - namespace.yaml
+  - repository.yaml
+  - release.yaml

infrastructure/prometheus/namespace.yaml

+apiVersion: v1
+kind: Namespace
+metadata:
+  name: monitoring
+  labels:
+    name: monitoring

infrastructure/prometheus/release.yaml

+apiVersion: helm.toolkit.fluxcd.io/v2beta1
+kind: HelmRelease
+metadata:
+  name: kube-prometheus
+  namespace: monitoring
+spec:
+  releaseName: monitoring
+  chart:
+    spec:
+      chart: kube-prometheus-stack
+      sourceRef:
+        kind: HelmRepository
+        name: prometheus-community
+      version: 19.0.2
+  interval: 5m

infrastructure/prometheus/repository.yaml

+apiVersion: source.toolkit.fluxcd.io/v1beta1
+kind: HelmRepository
+metadata:
+  name: prometheus-community
+spec:
+  interval: 30m
+  url: https://prometheus-community.github.io/helm-charts