refactor: Streamline abort handling and integrate GenerationJobManager for improved job management

- Removed the abortControllers middleware and integrated abort handling directly into GenerationJobManager.
- Updated abortMessage function to utilize GenerationJobManager for aborting jobs by conversation ID, enhancing clarity and efficiency.
- Simplified cleanup processes and improved error handling during abort operations.
- Enhanced metadata management for jobs, including endpoint and model information, to facilitate better tracking and resource management.

packages/api/src/stream/index.ts

@@ -1 +1,2 @@
 export { GenerationJobManager, GenerationJobManagerClass } from './GenerationJobManager';
+export type { AbortResult, SerializableJobData, JobStatus } from './interfaces/IJobStore';