Add possibility do add common labels in helm chart

[d-mankowski-synerise]

Is your feature request related to a problem? Please describe.

A lot of Helm charts (e.g. kube-prometheus-stack, cert-manager) allow to define key commonLabels, which results in a set of custom labels added to every resource created by the chart (pods, deployments, statefulsets, ingresses, services, servicemonitors, crds, etc.). Right now it is not even possible to add custom labels to Mimir's deployments or statefulsets (other than by using kustomize).

Use case: e.g. we want to have generic alerts (like: pod is crashlooping) that are dynamically routed, based on the label team (on the same cluster there is stuff deployed by various teams)

Describe the solution you'd like

In values.yaml we should be able to specify something like this:

commonLabels:
  label1: value1
  label2: value2

and all resources created by Mimir chart will have those labels

[Rohlik]

This is necessary for having common alerts and route them based on label(s). Having the option (below) to add labels to just pods is not enough.

global:
  podLabels:
    owner: best_team