Add printoptions

[ChristophePRAT]

Proposed changes

Add minimal print options similar to numpy's set_printoptions.

This PR should fix #471.

Quick example

import mlx.core as mx

a = mx.array([0.3668831623])

print(a) # 0.3668831623

with mx.printoptions(precision=2):
    print(a) # 0.37

print(a) # 0.3668831623

mx.set_printoptions(precision=4)
print(a) # 0.3669
print(a) # 0.3669

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

[zcbenz]

Can you make the API take a struct instead, for future extension?

[zcbenz]

For the C++ code we don't add __.

Suggested change

	void __exit__(nb::args) {
	void exit(nb::args) {

[zcbenz]

Can you move the print APIs to a new print.cpp file? The array.cpp is already bloated.

[zcbenz]

Can you fix the warning when building docs?

/home/runner/work/mlx/mlx/docs/src/python/printoptions.rst:2: WARNING: Title underline too short.