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• The pull request must only fix one issue at the time.
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What does this PR do?

This PR adds the hostname information to the CI Visibility trace using the _dd.hostname tag for Jenkins workers.

To do so, we read the environment variable DD_CI_HOSTNAME that must have been set in the worker previously. In case that envvar is not present, we set the _dd.hostname to none because we don't want to use the controller hostname (If we don't send hostname, it will be overridden by the DD Agent)

Description of the Change

Alternate Designs

Possible Drawbacks

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Review checklist (to be filled by reviewers)

• Feature or bug fix MUST have appropriate tests (unit, integration, etc...)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.