Implementation of pickle, copy and deepcopy for Python arrays (#300 & #367). (#713)

* Implemented pickling and copy for Python arrays(#300 & #367)

* Fixing typos

* Pickle with NumPy arrays

* Pickle: workaround for bfloat16

* Revert "Pickle: workaround for bfloat16"

This reverts commit 25afe6bc09.

* Added an error when pickling bfloat16

* Update python/tests/test_array.py

Co-authored-by: Awni Hannun <awni.hannun@gmail.com>

* Update python/tests/test_array.py

Co-authored-by: Awni Hannun <awni.hannun@gmail.com>

* Update python/src/array.cpp

Co-authored-by: Awni Hannun <awni.hannun@gmail.com>

* Update python/src/array.cpp

Co-authored-by: Awni Hannun <awni.hannun@gmail.com>

* clang-format applied

---------

Co-authored-by: Awni Hannun <awni.hannun@gmail.com>

ACKNOWLEDGMENTS.md

@@ -13,6 +13,7 @@ MLX was developed with contributions from the following individuals:
 - Diogo Da Cruz: Added `tri`, `tril`, `triu`, `tensordot`, `inner`, `outer`, `tile`, `StreamContext`, `stream` and safetensor support.
 - Gabrijel Boduljak: Added `mlx.core.linalg`, implemented `norm` method and `InstanceNorm` layer. Implemented pooling layers and ``Upsample``.
 - Hinrik Snær Guðmundsson: Added `atleast_1d`, `atleast_2d`, `atleast_3d` ops.
+- Luca Arnaboldi: Added `Ceil` and `Floor` ops; implemented pickling, copy and deepcopy for mlx arrays.
 - Brian Keene & Atila Orhon, with Argmax Inc.: Added `fast.scaled_dot_product_attention`
 <a href="https://github.com/ml-explore/mlx/graphs/contributors">
   <img class="dark-light" src="https://contrib.rocks/image?repo=ml-explore/mlx&anon=0&columns=20&max=100&r=true" />