Refactor exists

[SpyingEnvelope]

PR Description

The docstrings, examples, hint types, and arguments for exists were mostly correct. I turned the passed in parameter to be positional only, as per the recommendations from the Ivy documentation.

I also implemented an ivy.Container instance method for exists that returns an ivy.Container detailing if any of the leaves are None.

Related Issue

This should resolve issue #22937 for reformatting exists.

Checklist

• Did you add a function?
• Did you add the tests? - I added docstrings tests
• Did you follow the steps we provided?

Checklist provided by docs

• Remove all lambda and direct bindings for the backend functions (in ivy.functional.backends), with each function instead defined using def.
• Implement the following if they don’t exist but should do: ivy.Array instance method, ivy.Container instance method, ivy.Array special method, ivy.Array reverse special method, ivy.Container special method, ivy.Container reverse special method.
• Make sure that the aforementioned methods are added into the correct category-specific parent class, such as ivy.ArrayWithElementwise, ivy.ContainerWithManipulation etc.
• Correct all of the Function Arguments and the type hints for every function and its relevant methods, including those you did not implement yourself.
• Add the correct Docstrings to every function and its relevant methods, including those you did not implement yourself.
• Add thorough Docstring Examples for every function and its relevant methods and ensure they pass the docstring tests.

[github-actions]

Thanks for contributing to Ivy! 😊👏
Here are some of the important points from our Contributing Guidelines 📝:
1. Feel free to ignore the run_tests (1), run_tests (2), … jobs, and only look at the display_test_results job. 👀 It contains the following two sections:
- Combined Test Results: This shows the results of all the ivy tests that ran on the PR. ✔️
- New Failures Introduced: This lists the tests that are passing on main, but fail on the PR Fork. Please try to make sure that there are no such tests. 💪
2. The lint / Check formatting / check-formatting tests check for the formatting of your code. 📜 If it fails, please check the exact error message in the logs and fix the same. ⚠️🔧
3. Finally, the test-docstrings / run-docstring-tests check for the changes made in docstrings of the functions. This may be skipped, as well. 📚
Happy coding! 🎉👨‍💻

[AnnaTz]

Thanks, looks good!