feat(streaming): emit OTel metrics for ttft, tps, token counts #1485

Job	Run time
find-tutorials	6s
test-10_async/10_temporal/030_custom_activities	1m 58s
test-10_async/00_base/000_hello_acp	2m 11s
test-00_sync/000_hello_acp	1m 55s
test-10_async/10_temporal/070_open_ai_agents_sdk_tools	2m 11s
test-10_async/10_temporal/010_agent_chat	2m 50s
test-10_async/00_base/030_tracing	1m 58s
test-10_async/00_base/010_multiturn	2m 8s
test-10_async/10_temporal/060_open_ai_agents_sdk_hello_world	2m 3s
test-10_async/00_base/040_other_sdks	4m 11s
test-00_sync/010_multiturn	3m 42s
test-10_async/10_temporal/020_state_machine	2m 39s
test-00_sync/020_streaming	2m 31s
test-10_async/10_temporal/090_claude_agents_sdk_mvp	1m 59s
test-00_sync/030_langgraph	3m 10s
test-10_async/10_temporal/050_agent_chat_guardrails	1m 49s
test-10_async/00_base/100_langgraph	2m 4s
test-10_async/00_base/020_streaming	2m 17s
test-10_async/10_temporal/080_open_ai_agents_sdk_human_in_the_loop	2m 0s
test-10_async/00_base/080_batch_events	3m 32s
test-10_async/10_temporal/000_hello_acp	2m 10s
Test Summary	7s
	49m 31s

Provide feedback