fix(ddtrace/tracer): Implement Serverless Service Representation

[ojproductions]

What does this PR do?

Fixes the Serverless Service Representation (SSR) for Go.
In serverless environments, sets peer.service tag for AWS managed service spans to {service type}.{region}.amazonaws.com:

• SQS: sqs.us-east-1.amazonaws.com
• SNS: sns.us-east-1.amazonaws.com
• Kinesis: kinesis.us-east-1.amazonaws.com
• Eventbridge: events.us-east-1.amazonaws.com
• s3: bucket-name.s3.us-east-1.amazonaws.com
• Dynamodb: dynamodb.us-east-1.amazonaws.com

Sets peer.service.source to peer.service for these serverless cases.
Adds LambdaFunctionName as field in tracer config to detect serverless cases.

Motivation

Prior to changes:

After changes: View represents customers' mental model of systems better.

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.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-10-22 16:36:32

Comparing candidate commit e42f255 in PR branch APMSVLS-39 with baseline commit d6f7d92 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 24 metrics, 0 unstable metrics.

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: e42f255 | Docs | Was this helpful? Give us feedback!}

[zarirhamza]

Overall looks good, just some code quality changes

[zarirhamza]

LGTM - nice change on the serverless check to improve performance

[darccio]

Approved, but consider @purple4reina's feedback in https://github.com/DataDog/dd-trace-go/pull/4043/files#r2449442341.

[genesor]

LGTM

[rithikanarayan]

/merge

[dd-devflow-routing-codex]

View all feedbacks in Devflow UI.

2025-10-22 17:13:25 UTC ℹ️ Start processing command /merge

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2025-10-22 17:13:30 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in main is approximately 18m (p90).

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2025-10-22 17:28:30 UTC ℹ️ MergeQueue: This merge request was merged