Enable Prometheus /metrics endpoint

[JohnStarich]

Adds prometheus /metrics endpoint and ServiceMonitor configuration, which Prometheus Operator can pick up. Requires RBAC authentication to use it. Details in the kubebuilder handbook. Essentially need to run this to configure access manually:

kubectl create clusterrolebinding metrics --clusterrole=ibmcloud-operators-metrics-reader --serviceaccount=<namespace>:<service-account-name>

After injecting a debug container, I was able to display the raw metrics:

Fixes #122

[codecov]

Codecov Report

Merging #177 into master will increase coverage by 1.88%.
The diff coverage is 43.34%.

@@            Coverage Diff             @@
##           master     #177      +/-   ##
==========================================
+ Coverage   41.46%   43.34%   +1.88%     
==========================================
  Files          13        5       -8     
  Lines        1423      879     -544     
==========================================
- Hits          590      381     -209     
+ Misses        714      411     -303     
+ Partials      119       87      -32     

Impacted Files	Coverage Δ
controllers/configmap.go	0.00% <0.00%> (ø)
controllers/secret.go	25.00% <25.00%> (ø)
controllers/binding_controller.go	37.88% <37.88%> (ø)
controllers/service_controller.go	48.71% <48.71%> (ø)
controllers/token_controller.go	74.13% <74.13%> (ø)

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[vazirim]

LGTM