Batching of BatchNorm* Ops is Busted

BatchNorm Ops don't natively support batching if we are also batching the mean/var/scale/bias. We can decompose the op and batch the resulting ops

Start by locating the BatchNorm* operation handling and the batching logic for mean, variance, scale, and bias. Determine how to decompose the operation so these inputs can be batched, then verify that batched BatchNorm operations produce the expected result.

Written by the indexing model from the issue text.