fix(llmobs): fix llmobs to apm link for spans

[rarguelloF]

What does this PR do?

We were not attaching the apm span trace id (+ other info) to the llmobs span events, so the View in APM button in the LLMObs trace/span view was not showing up.

Motivation

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• New code is free of linting errors. You can check this by running ./scripts/lint.sh locally.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-11-20 11:32:27

Comparing candidate commit 4d7ea15 in PR branch rarguelloF/fix-llmobs-apm-link with baseline commit 61f9647 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 15 metrics, 0 unstable metrics.

[rarguelloF]

/merge

[dd-devflow-routing-codex]

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2025-11-07 13:09:39 UTC ℹ️ Start processing command /merge

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2025-11-07 13:09:48 UTC ℹ️ MergeQueue: waiting for PR to be ready

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2025-11-07 17:10:08 UTC ⚠️ MergeQueue: This merge request was unqueued

devflow unqueued this merge request: It did not become mergeable within the expected time

[rarguelloF]

/merge

[dd-devflow-routing-codex]

View all feedbacks in Devflow UI.

2025-11-20 11:12:40 UTC ℹ️ Start processing command /merge

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2025-11-20 11:12:48 UTC ℹ️ MergeQueue: waiting for PR to be ready

This pull request is not mergeable according to GitHub. Common reasons include pending required checks, missing approvals, or merge conflicts — but it could also be blocked by other repository rules or settings.
It will be added to the queue as soon as checks pass and/or get approvals.
Note: if you pushed new commits since the last approval, you may need additional approval.
You can remove it from the waiting list with /remove command.

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2025-11-20 12:07:25 UTC ℹ️ MergeQueue: merge request added to the queue

The expected merge time in main is approximately 32m (p90).

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2025-11-20 12:29:30 UTC ℹ️ MergeQueue: This merge request was merged