Use ArcArray in `ndarray` backend

[statusfailed]

Problem

catgrad's interpreter::backend::Backend generally assumes that ops take ownership of tensors.
This means they can deallocate them, or even re-use input tensors to write outputs, avoiding allocating additional memory.

However, parameters cannot have ownership transferred without (inefficiently) cloning the whole tensor.

Task

Change Backend::NdArray type for ndarray backend to use ArcArrayD instead (so we can cheaply clone parameter tensors).

Outcome

• Patched ndarray backend using ArcArrayD for its NdArray type
• Criterion Benchmark showing improvement over baseline (current) implementation

[janimo]

Parameters are no longer copied when cloned, the ndarray backend uses ArcArray inside the TaggedArrayD. All the other backend methods still use ArrayD and owned copies.