Reorganize `tensor.basic.py` and `tensor.math.py`.

[ricardoV94]

Description

These two are doing way too much. We should probably split more along the lines of how we listed #821 if not more fine-grained.

• Elemwise (which DimShuffle is not!)
• Reduce: CAReduce + Argmax
• Alloc (or tensor_creation or something): Ops that create tensors (Alloc, AllocEmpty, Diagonal, Arange, ...)

basic and math are just too big and vague. Also the rewrites should be restructured a bit to reflect the changes, although it's sometimes tricky when you are rewriting Elemwise + Reduce or Elemwise + Alloc, Probably we can put it in the non-elemwise, since that's more specific