feat: add when-then-otherwise expression

[aivanoved]

What type of PR is this? (check all applicable)

• 💾 Refactor
• ✨ Feature
• 🐛 Bug Fix
• 🔧 Optimization
• 📝 Documentation
• ✅ Test
• 🐳 Other

Related issues

• Related issue add when-then-otherwise #47

Checklist

• Code follows style guide (ruff)
• Tests added
• Documented the changes

If you have comments or can explain your changes, please do so below.

This PR so far adds a simple when-then-otherwise expression with no chaining

The PR does not aim to be complete as of now, the current aim is to get an initial review as to if this approach is consistent with the project's quality and style of code

TODO:

• Allow Iterable[IntoPandasExpr] to the pandas API for predicates
• Allow when-then-otherwise chaining obsolete: see comments below and enh: improve when-then-otherwise to include chaining #668
• Address noqa ignores

Note: Temporary converted back to draft due to a git rebase issue fixed

Note: due to an unfortunate rebase gone wrong, the commit history is a mess, we could open a new pr from a new branch or when merging do a squash merge. Further advice on this would be much appreciated.

[aivanoved]

fixed by xfail current ci fails with the new zip_with, due to a known issue in modin, here

fixed ci fails because of this if conditioning, which is essentially a pandas version check, so the else condition does not get executed for pandas>=1.*, for me this is a tricky one to fix.failure due to coverage test

[MarcoGorelli]

thanks @aivanoved ! I just pushed some slight changes to avoid using nullable dtypes when the user didn't ask for them

[EdAbati]

Thank you @aivanoved for working this! This is a great addition