What does this PR do?

Makes the classes that serialize pipelines to webhooks generate a span id and trace id, similar to the classes that serialize to traces.

Description of the Change

datadog-ci relies on us setting the trace and span ids as env vars, which wasn't working for Agentless (sending webhooks instead of traces). We already have code to set these env vars and they are correctly populated since this uses the same logic we have in the classes that generate traces.

Verification Process

• Run with finer level logging so the payloads are printed and verify that job, stage and pipeline webhook payloads contain span_id and trace_id (and that trace_id is the same for all the jobs from a same pipeline).
• Print $DD_CUSTOM_TRACE_ID and $DD_CUSTOM_PARENT_ID in a job and check they the trace and span ids from the payloads.

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.