[cleanup] rm v2 from function names in metrics forwarder

[celenechang]

What does this PR do?

Additional cleanup following v1alpha2 deprecation

Motivation

What inspired you to submit this pull request?

Additional Notes

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Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

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

Describe your test plan

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Checklist

• 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

Attention: Patch coverage is 22.22222% with 7 lines in your changes missing coverage. Please review.

Project coverage is 47.34%. Comparing base (46c0dd2) to head (630fb6b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1313   +/-   ##
=======================================
  Coverage   47.34%   47.34%           
=======================================
  Files         230      230           
  Lines       22027    22027           
=======================================
  Hits        10429    10429           
  Misses      11008    11008           
  Partials      590      590           

Flag	Coverage Δ
unittests	47.34% <22.22%> (ø)

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Files	Coverage Δ
pkg/controller/utils/datadog/metrics_forwarder.go	31.07% <22.22%> (ø)

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