fix: k8s version detection for agent service

[clamoriniere]

What does this PR do?

Fix how we detect the Kubernetes version.
the information was already present in the reconciler.

the manageAgentService() function now use the information
from the Reconcile struct.

Motivation

Fix how we detect the Kubernetes version to automaticaly
create the local agent service if it is supported by the
kubernetes version.

Additional Notes

Describe your test plan

deploy the operator and create the DatadogAgent with this manifest

apiVersion: datadoghq.com/v1alpha1
kind: DatadogAgent
metadata:
  name: datadog
spec:
  agent:
    apm:
      enabled: true
  clusterName: foo
  credentials:
    apiSecret:
      keyName: api-key
      secretName: datadog-secret
    appSecret:
      keyName: app-key
      secretName: datadog-secret

the service datadog-agent should be created in the same namespace.

[codecov-commenter]

Codecov Report

Merging #472 (2a4f1c8) into main (b9ad1fc) will increase coverage by 2.43%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #472      +/-   ##
==========================================
+ Coverage   60.60%   63.04%   +2.43%     
==========================================
  Files           3        3              
  Lines         132      138       +6     
==========================================
+ Hits           80       87       +7     
+ Misses         40       38       -2     
- Partials       12       13       +1     

Flag	Coverage Δ
unittests	63.04% <ø> (+2.43%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
controllers/datadogagent_controller.go	64.38% <0.00%> (+4.68%)	⬆️

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