Batcher simplifications

[declark1]

While working on the chat completion detection streaming implementation, I realized that we can simplify some things related to the batcher. As the ChatCompletionBatcher implementation ended up being simpler than expected, we do not actually need generic batches. It's essentially the same as the MaxProcessedIndexBatcher (a single batcher could actually be used for both), but we can keep separate implementations in case chat completion batching requirements evolve.

Changes related to this:

• Drop associated type Batch from DetectionBatcher and Batch generics throughout
• Add Batch = (u32, Chunk, Detections) type alias; we can use this for all batchers
• Integrate single detection stream optimization into DetectionBatchStream and drop process_detection_stream() functions
  • We only need process_batch_detection_stream() now rather than separate functions
  • We couldn't integrate this previously because DetectionBatchStream returned a generic type, while DetectionStream returned a static type (even if they are the same)

Other changes:

• Drop detector_id from DetectionStream and DetectionBatcher::push(); it's redundant as detector_id is set in Detection
• Drop NoopBatcher (not needed for testing)
• Drop InputId type alias and just use u32