implemented InstanceNorm (#244)

* implemented instancenorm

* implemented vector_norm in cpp

added linalg to mlx

* implemented vector_norm python binding

* renamed vector_norm to norm, implemented norm without provided ord

* completed the implementation of the norm

* added tests

* removed unused import in linalg.cpp

* updated python bindings

* added some tests for python bindings

* handling inf, -inf as numpy does, more extensive tests of compatibility with numpy

* added better docs and examples

* refactored mlx.linalg.norm bindings

* reused existing util for implementation of linalg.norm

* more tests

* fixed a bug with no ord and axis provided

* removed unused imports

* some style and API consistency updates to linalg norm

* remove unused includes

* fix python tests

* fixed a bug with frobenius norm of a complex-valued matrix

* complex for vector too

* addressed PR review comments

* fixed import order in __init__

* expected values in instancenorm tests are simple lists

* minor return expression style change

* added InstanceNorm to docs

* doc string nits

* added myself to individual contributors

---------

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

docs/src/python/nn/layers.rst

@@ -26,6 +26,7 @@ Layers
    LayerNorm
    RMSNorm
    GroupNorm
+   InstanceNorm
    Dropout
    Dropout2d
    Dropout3d