Feature Request: add an additional argument to auto_optim to allow for gradient accumulation

When we use horovod backend and perform gradient accumulation, we get the following error: AssertionError: Gradients were computed more than backward_passes_per_step times before call to step(). Increase backward_passes_per_step to accumulate gradients locally.

Thus, we need to change the default argument backward_passes_per_step of horovod.DistributedOptimizer to enable gradient accumulation in the distributed setting. To do so, we can add this argument to ignite.distributed.auto_optim.

[Chandan-h-509]

ohk… Got it… Can i work on it?

[vfdev-5]

@sandylaker thanks for the feature request ! Maybe, we can enable kwargs for auto_optim as it is done for auto_model. In the docs we can explicitly say where kwargs goes exactly.