Fix Kubernetes labels normalization for Prometheus

[slok]

PR info

Continues from #7374

When we were testing v2.2.0-rc1 and added the label metrics, Argo panicked because of the type of labels we use (Valid in Kubernetes). We use organization.fonoa.io/owner style labels. This was the error:

panic: descriptor Desc{fqName: "argocd_app_labels", help: "Argo Application labels converted to Prometheus labels", constLabels: {}, variableLabels: [namespace name project l
abel_organization.fonoa.io/owner label_runtime.fonoa.io/cluster label_runtime.fonoa.io/environment label_runtime.fonoa.io/service label_runtime.fonoa.io/tier]} is invalid: "l
abel_organization.fonoa.io/owner" is not a valid label name for metric "argocd_app_labels"

This PR solves this by replacing all non-valid Prometheus labels characters with a _ character.

Checklist

This PR is a small fix that

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[leoluz]

LGTM

[codecov]

Codecov Report

Merging #7925 (1ae77cf) into master (bed36e2) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #7925   +/-   ##
=======================================
  Coverage   41.48%   41.48%           
=======================================
  Files         169      169           
  Lines       22353    22353           
=======================================
  Hits         9274     9274           
  Misses      11755    11755           
  Partials     1324     1324           

Impacted Files	Coverage Δ
controller/metrics/metrics.go	80.00% <100.00%> (ø)

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