[Cleanup] Cleanup unused parts from datasets

[Cleanup] Cleanup unused parts from datasets

**Changes proposed in this PR:**
- batch_queue.[h|cpp] -> iteration_queue.[h|cpp]
- delete Class BatchcQueue
- delete Producer::finalize, Producer::size,
databuffer::startFetchWorker, databuffer::fetch and following patch
- delete DataProducer::Iteration, DataProducer::Sample as we have
dedicated classes instead.
- remove *_sample suffix. (eg) DataProducer::finalize_sample becomes
DataProducer::finalize)

**Self evaluation:**
1. Build test: [X]Passed [ ]Failed [ ]Skipped
2. Run test: [X]Passed [ ]Failed [ ]Skipped

Signed-off-by: Jihoon Lee <jhoon.it.lee@samsung.com>