Update v1alpha1 deprecation log line

[levan-m]

What does this PR do?

Switched to ERROR log and indicated versions of flag and CRD deprecation, first line of Operator log when v2APIEnabled is set to false.

{"level":"INFO","ts":"2024-02-23T17:23:01Z","logger":"setup","msg":"Version: v1.4.0-rc.3_910ccf3f"}
{"level":"INFO","ts":"2024-02-23T17:23:01Z","logger":"setup","msg":"Build time: 2024-02-23/12:19:48"}
{"level":"INFO","ts":"2024-02-23T17:23:01Z","logger":"setup","msg":"Git Commit: 910ccf3"}
{"level":"INFO","ts":"2024-02-23T17:23:01Z","logger":"setup","msg":"Go Version: go1.19.13"}
{"level":"INFO","ts":"2024-02-23T17:23:01Z","logger":"setup","msg":"Go OS/Arch: linux/arm64"}
{"level":"ERROR","ts":"2024-02-23T17:23:01Z","logger":"setup","msg":"The 'v2APIEnabled' flag is deprecated since v1.2.0+ and will be removed in a v1.7.0. Once removed, the Datadog Operator cannot be configured to reconcile the v1alpha1 DatadogAgent CRD. However, you will still be able to apply a v1alpha1 manifest with the conversion webhook enabled (using the flag 'webhookEnabled'). DatadogAgent v1alpha1 and conversion webhook hook will be removed from v1.8.0. See migration page for more details https://docs.datadoghq.com/containers/guide/datadogoperator_migration/"}
{"level":"INFO","ts":"2024-02-23T17:23:01Z","logger":"setup","msg":"Manager will be watching namespace","namespace":"system"}

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Additional Notes

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Minimum Agent Versions

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• Agent: vX.Y.Z
• Cluster Agent: vX.Y.Z

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• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.71%. Comparing base (bb82660) to head (4f6058f).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1099      +/-   ##
==========================================
+ Coverage   58.65%   58.71%   +0.06%     
==========================================
  Files         173      173              
  Lines       21129    21155      +26     
==========================================
+ Hits        12393    12421      +28     
  Misses       7984     7984              
+ Partials      752      750       -2     

Flag	Coverage Δ
unittests	58.71% <ø> (+0.06%)	⬆️

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[celenechang]

Suggested change

	"DatadogAgent v1alpha1 and conversion webhook hook will be removed from v1.8.0. "+
	"DatadogAgent v1alpha1 and the conversion webhook will be removed from v1.8.0. "+