Handle telemetry in non-interactive mode (#1002)

Changes:
- Ensure proper shutdown in non-interactive mode
- Ensures the initial user prompt is logged in non-interactive mode
- Improve telemetry for streaming - handle chunks and input token count is now alongside other token counts in response

To test:
- Follow instructions in https://github.com/google-gemini/gemini-cli/blob/main/docs/core/telemetry.md#google-cloud
- Run CLI in non-interactive mode and observe logs/metrics in GCP Logs Explorer and Metrics Explorer

#750

packages/core/src/telemetry/index.ts

@@ -16,6 +16,7 @@ export {
   logApiRequest,
   logApiError,
   logApiResponse,
+  combinedUsageMetadata,
 } from './loggers.js';
 export {
   UserPromptEvent,