support service address and implement span links

[nikhilNava]

Task
Add baggage builder method to support server address and port. Required for auto instrumentation.
Add span links to support async spans

[github-actions]

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[Copilot]

Pull request overview

This PR extends the observability core SDK to support (1) propagating target server address/port via baggage for invoke-agent scenarios (to help auto-instrumentation), and (2) attaching OpenTelemetry span links to spans to represent causal relationships across async work.

Changes:

• Add BaggageBuilder.invoke_agent_server(address, port) and propagate server.address / server.port onto invoke_agent spans via the span processor.
• Add SpanDetails.span_links and wire span links through OpenTelemetryScope into OTel span creation.
• Refactor scope/span creation to use SpanDetails (notably span kind) and add test coverage for span links and server address/port baggage propagation.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
tests/observability/core/test_span_links.py	New tests validating that SpanDetails.span_links are forwarded to OTel spans across scope types.
tests/observability/core/test_record_attributes.py	Updates tests to pass span kind via SpanDetails instead of string kind=.
tests/observability/core/test_invoke_agent_scope.py	Adds test asserting server address/port baggage is propagated onto invoke-agent spans.
tests/observability/core/test_baggage_builder.py	Adds tests for the new invoke_agent_server() baggage builder method.
libraries/.../trace_processor/util.py	Updates the attribute allowlists used by the baggage-to-span span processor; adds server address/port to invoke-agent attributes.
libraries/.../spans_scopes/output_scope.py	Switches OutputScope to pass SpanDetails (and span links) into OpenTelemetryScope.
libraries/.../span_details.py	Adds span_links to SpanDetails.
libraries/.../opentelemetry_scope.py	Refactors constructor to accept SpanDetails and passes links= into tracer.start_span(...).
libraries/.../middleware/baggage_builder.py	Adds invoke_agent_server(address, port) to set server address/port baggage.
libraries/.../invoke_agent_scope.py	Refactors InvokeAgentScope span creation to use SpanDetails (including span links).
libraries/.../inference_scope.py	Refactors InferenceScope span creation to use SpanDetails (including span links).
libraries/.../execute_tool_scope.py	Refactors ExecuteToolScope span creation to use SpanDetails (including span links).

[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.