setup exporter as creating executor. Then we could skip setup in many…

… positions.

And remove setup for process pool

src/promptflow-core/promptflow/executor/_line_execution_process_pool.py

@@ -696,11 +696,6 @@ def _process_wrapper(
         bulk_logger.info("Current thread is not main thread, skip signal handler registration in batch process pool.")
     OperationContext.get_instance().update(operation_contexts_dict)  # Update the operation context for the new process.
 
-    # set up OpenTelemetry exporter in process who executes the line
-    from promptflow.tracing._start_trace import setup_exporter_from_environ
-
-    setup_exporter_from_environ()
-
     _exec_line_for_queue(
         executor_creation_func,
         output_dir,