[Backport v1.27] fix(dogstatsd): always set DSD environment variables on Core Agent container

[dd-octo-sts]

Backport efb068e from #3032.

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What does this PR do?

This PR updates the dogstatsd feature to set the relevant DSD-specific environment variables on the Core Agent container whether or not ADP is enabled.

Motivation

Originally, based on how ADP worked, we needed to do the conditional split: add DSD settings directly on the ADP container when enabled. However, with ADP 1.0.0, this has changed: Core Agent authoritatively provides configuration to ADP, and so we want all configuration to be provided to the Core Agent, which then provides it to ADP.

As such, we need to move these environment variables back to the Core Agent container to ensure they flow to ADP as intended.

Additional Notes

Anything else we should know when reviewing?

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

To be updated.

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
• All commits are signed (see: signing commits)

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[chatgpt-codex-connector]

Preserve DogStatsD port binding in single-container mode

When global.containerStrategy is single, ManageSingleContainerNodeAgent calls manageNodeAgent with unprivileged-single-agent, but this branch unconditionally rewrites the port target to agent-data-plane whenever Data Plane DogStatsD is enabled. In real reconciliation, AddPortToContainer only mutates existing containers, so on single-container pods (no agent-data-plane container) the DogStatsD ContainerPort/HostPort is dropped entirely, which regresses the previous behavior and breaks DogStatsD host-port exposure for that configuration.

Useful? React with 👍 / 👎.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 41.37%. Comparing base (8e158b7) to head (ef15977).

Files with missing lines	Patch %	Lines
...ntroller/datadogagent/feature/dogstatsd/feature.go	94.73%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            v1.27    #3034   +/-   ##
=======================================
  Coverage   41.36%   41.37%           
=======================================
  Files         334      334           
  Lines       28586    28581    -5     
=======================================
  Hits        11826    11826           
+ Misses      15970    15965    -5     
  Partials      790      790           

Flag	Coverage Δ
unittests	41.37% <94.73%> (+<0.01%)	⬆️

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

Files with missing lines	Coverage Δ
...ntroller/datadogagent/feature/dogstatsd/feature.go	75.00% <94.73%> (+2.27%)	⬆️

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[datadog-prod-us1-3]

🎯 Code Coverage (details)
• Patch Coverage: 95.00%
• Overall Coverage: 41.70% (+0.01%)

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