apply_batch to batch_size in Agent class

[riddhipits]

Currently, the class uses a boolean parameter apply_batch to determine whether to apply batching to the ABCD etc tensors. I suggest replacing this boolean with a batch_size parameter, which would default to 1. This change would allow for more flexibility in handling batch sizes while maintaining backward compatibility. Setting the default value of batch_size to 1 ensures that users who do not wish to use batching can continue to work with the library without any changes to their existing code.