Upgrade Datadog tracer to dd-trace-go v2

[yarinzirlin]

• Updated imports from v1 (gopkg.in/DataDog/dd-trace-go.v1) to v2 (github.com/DataDog/dd-trace-go/v2)
• Updated struct types to use pointers (*tracer.Span, *tracer.SpanContext) as required by v2
• Replaced deprecated ChildOf() pattern with modern v2 approach:
  • Use Span.StartChild() for direct parent spans
  • Use tracer.WithStartSpanConfig() for span contexts
• Updated tests to handle v2 API changes (pointer types for mocktracer.Span)
• Removed unused helper functions (newSpanContextReader, spanContextReader)
• All tests passing

This upgrade ensures compatibility with the latest Datadog APM features and removes dependency on deprecated v1 APIs.

What was changed

Updated dd-trace-go from the deprecated v1 to v2

Why?

1. dd-trace-go v1 stopped working

Checklist

1. How was this tested:
   I ran the upgraded interceptor against my Datadog instance and saw the expected traces

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[hferentschik]

+1 for switching to dd-trace-go v2

[Quinn-With-Two-Ns]

Just a quick update, the data dog tracing module was contributed by an external team and we are currently reaching out to them to review this change.

[jlegrone]

There are two breaking changes here. They won't impact all users, but:

• Anyone specifying a TracerOptions.OnFinish function will need to modify their imports from gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer to github.com/DataDog/dd-trace-go/v2/ddtrace/tracer. The old and new versions of this type are source compatible however, so no other changes are needed.
• Anyone using the SpanFromWorkflowContext function will need to modify their code to reference the new type if they pass the returned span into a function accepting the old ddtrace.Span type, or if they were calling the Context() method.

Breaking changes are technically ok to do without releasing a v2 of this module, since we are still on a pre-stable version (v0.4.0). I think it is acceptable to release this as v0.5.0 as long as we document these breaking changes in the release notes. If necessary, we should still be able to backport bugfixes by tagging a v0.4.1 version.

@yarinzirlin would you like to take a stab at writing the release notes for this version?

[yuandrew]

Thanks for the contribution!