ekump/APMSP-2153 break up large trace exporter functions (#1142)

* move trace exporter builder to separate file

* break down send_trace_chunks_inner into smaller functions

* break down agent response and info functions into smaller ones

* break down handle_send_result function into smaller ones

* break down run_worker function into smaller ones

* break down start_stats_computation and prepare_traces_payload function into smaller ones

* break down handle_http_error_response function that we just created into smaller ones

* break down send_data_to_url function into smaller ones

* break down build_trace_request function into smaller ones

Author: ekump