feat(otel): add --otel_to_cloud experimental support

Cloud Trace, Cloud Monitoring and Cloud Logging integrations are set up via OTel if otel_to_cloud CLI param/fast_api arg is provided.

This is similar to current Cloud Trace integration via trace_to_cloud, just extended to Monitoring and Logging as well.

PiperOrigin-RevId: 807385680

tests/unittests/telemetry/test_functional.py

@@ -16,10 +16,10 @@ import gc
 import sys
 from unittest import mock
 
-from google.adk import telemetry
 from google.adk.agents import base_agent
 from google.adk.agents.llm_agent import Agent
 from google.adk.models.base_llm import BaseLlm
+from google.adk.telemetry import tracing
 from google.adk.tools import FunctionTool
 from google.adk.utils.context_utils import Aclosing
 from google.genai.types import Part
@@ -74,7 +74,7 @@ def mock_start_as_current_span(monkeypatch: pytest.MonkeyPatch) -> mock.Mock:
         tracer, 'start_as_current_span', mock_start_as_current_span
     )
 
-  do_replace(telemetry.tracer)
+  do_replace(tracing.tracer)
   do_replace(base_agent.tracer)
 
   return mock_start_as_current_span