Add support for numpy scalar and boolean mask indexing

[cetagostini]

Proposed changes

Enhanced indexing logic to handle numpy scalar types and boolean masks in mlx arrays. Updated C++ implementation to convert boolean masks to integer indices and support numpy scalar types in indexing and assignment. Added comprehensive tests for numpy scalar and boolean mask indexing behaviors.

Solve issue: #2710

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)

[cetagostini]

Hey MLX team, thanks for the awesome library. Opening this to actually get better support of certain indexing things into pytensor, which allow now MLX backend :)

cc: @awni @angeloskath

[cetagostini]

Hey guys, did you had a chance to take a look here? @awni @angeloskath

[awni]

Thanks for the contribution!

The boolean indexing conflicts with #2663. Could you please remove it and we will land it in #2663 ?

After that we can review the numpy scalar indexing addtion.