[java/google-adk] Support replay-safe native ADK tracing #258

Support ADK's native agent, model, and tool spans when an agent runs inside a Temporal Workflow. Temporal Workflow/Activity interceptor spans alone do not meet this requirement.

ADK Java 1.12.0's Tracing obtains its tracer from GlobalOpenTelemetry and creates native invoke_agent, call_llm, and execute_tool spans. With io.temporal:google-adk:0.1.0, agent orchestration and deterministic tools execute in Workflow code. The plugin has no replay suppression for those native spans, so installing an OpenTelemetry SDK can export them again during replay; this is a documented limitation.

Provide a supported way to configure native ADK tracing, suppress replay exports, and preserve trace context across model/tool Activity boundaries. Account for ADK's global tracer and context propagation across Workflow and RxJava threads without filtering unrelated application spans.

Acceptance criteria:

• Run a real ADK LlmAgent with a scripted model and both deterministic and Activity tools, exporting to an in-memory/local sink without provider credentials.
• Assert native ADK agent/model/tool operation names, useful ADK attributes, and their parent/child relationships. Temporal operation spans are optional and do not substitute for these assertions.
• Force replay through cache eviction, Worker restart, and fresh-Worker history replay. Export no duplicate native spans, preserve useful parentage when execution resumes, and avoid telemetry I/O during replay.
• Cover failed/retried model and tool calls, agent completion, and cancellation. Verify tracing configuration does not change Workflow commands or break replay of existing histories.
• Document exporter setup and add live/offline native-ADK observability samples once the published plugin supports this behavior.

The Temporal-operation tracing sample is being removed from samples-java #811 and documentation #5587.