Track prompt cache write token usage (#33454)

## What changed

- Parse `cache_write_tokens` from response input token details and carry it through token usage aggregation.
- Expose `cache_write_input_tokens` in protocol, app-server, exec, and TypeScript SDK usage events, defaulting it to zero for compatibility with older payloads.
- Report cache-write usage in analytics, metrics, traces, and rollout data alongside existing cache-read usage.

## Testing

- Add coverage for response parsing, usage event output, aggregation, analytics, metrics, and telemetry fields.

GitOrigin-RevId: 634e4fbe3086a8923c0ee13b622573e7d9d221bd

codex-rs/core/src/client.rs

@@ -2002,14 +2002,7 @@ where
                 }) => {
                     feedback_tags!(last_model_response_id = &response_id);
                     if let Some(usage) = &token_usage {
-                        session_telemetry.sse_event_completed(
-                            usage.input_tokens,
-                            usage.output_tokens,
-                            Some(usage.cached_input_tokens),
-                            Some(usage.reasoning_output_tokens),
-                            usage.total_tokens,
-                            ttft_ms,
-                        );
+                        session_telemetry.sse_event_completed(usage, ttft_ms);
                     }
                     inference_trace_attempt.record_completed(
                         &response_id,