Use the built-in instrumentor from google-adk

[saeedghadiri]

The Vertex AI google-adk package now includes a build_instrumentor() method.
Updated the documentation to use this official implementation instead of the AgentModule solution (which is not well-documented in vertex).

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Note

Update docs to use AdkApp with built-in instrumentor_builder for Agent Engine tracing and refresh env vars and examples.

• Docs (Google ADK Tracing):
  • Agent Engine deployment:
    • Switch from ModuleAgent + manual instrumentation to AdkApp with instrumentor_builder using arize.otel.register and GoogleADKInstrumentor.
    • Update env_vars for OTEL/Arize (OTEL_LOG_LEVEL, NO_PROXY, new OTEL_EXPORTER_OTLP_ENDPOINT, ARIZE_API_KEY, ARIZE_SPACE_ID, OTEL_EXPORTER_OTLP_TIMEOUT).
    • Simplify agent module example to define root_agent; instrumentation now configured in the main app via build_instrumentor.
  • Resources: Add link to VertexAI ADK template.

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[saeedghadiri]

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