CoW: Fix deprecation warning for chained assignment
- [ ] closes #xxxx (Replace xxxx with the GitHub issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

I hate the SettingWithCopyWarning mechanism...

2 cases were fixed here:

- the parent that holds the item_cache might be dead, e.g. the ref count is not increased. We have to check this when looking at the cacher
- iloc does not populate the item_cache but it sets _cacher on the new object, so we have to check if we are actually part of the item_cache

xref https://github.com/pandas-dev/pandas/issues/56019
> I hate the SettingWithCopyWarning mechanism...

Oh I am looking forward to ripping out all that code ;) Yes me too, I call dips on doing that :)