feat: Add mTLS support for telemetry endpoint.

This change enables the telemetry exporter to use mTLS endpoints when configured, by dynamically determining the correct endpoint and configuring the requests session accordingly. It introduces helper functions to handle client certificate source management.

PiperOrigin-RevId: 904002118

Author: vertex-sdk-bot

vertexai/agent_engines/templates/adk.py

@@ -818,11 +818,6 @@ def set_up(self):
         from google.adk.memory.in_memory_memory_service import InMemoryMemoryService
 
         os.environ["GOOGLE_GENAI_USE_VERTEXAI"] = "1"
-        # --- BEGIN BOUND TOKEN PATCH ---
-        # Set GOOGLE_API_PREVENT_AGENT_TOKEN_SHARING_FOR_GCP_SERVICES to false
-        # to disable bound token sharing.
-        os.environ["GOOGLE_API_PREVENT_AGENT_TOKEN_SHARING_FOR_GCP_SERVICES"] = "false"
-        # --- END BOUND TOKEN PATCH ---
         project = self._tmpl_attrs.get("project")
         if project:
             os.environ["GOOGLE_CLOUD_PROJECT"] = project