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/app-server/src/bespoke_event_handling.rs

@@ -3708,6 +3708,7 @@ mod tests {
             total_token_usage: TokenUsage {
                 input_tokens: 100,
                 cached_input_tokens: 25,
+                cache_write_input_tokens: 0,
                 output_tokens: 50,
                 reasoning_output_tokens: 9,
                 total_tokens: 200,
@@ -3715,6 +3716,7 @@ mod tests {
             last_token_usage: TokenUsage {
                 input_tokens: 10,
                 cached_input_tokens: 5,
+                cache_write_input_tokens: 0,
                 output_tokens: 7,
                 reasoning_output_tokens: 1,
                 total_tokens: 23,