DEPR: df.iloc[:, foo] = bar attempt to set inplace
- [x] closes #44353
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [x] whatsnew entry

can you rebase Made a couple of efforts recently to simplify the `iloc.__setitem__` and they all crash on the rocks of this inconsistency. There's a problem here in that the `use .iloc(axis=1)[foo]=bar` won't actually work, so still need a better alternative.

But getting this done should be a very high priority for 1.5 as its a blocker for all kinds of inconsistency-fixing. @jreback in the Feb call i think we agreed to move forward with this but there was some bikeshedding over the name of the replacement method.  Do you remember what we landed on? > @jreback in the Feb call i think we agreed to move forward with this but there was some bikeshedding over the name of the replacement method. Do you remember what we landed on?

`isetitem` I *think* > `isetitem` I think

cool, since thats what the PR implements ATM @jreback gentle ping, finally green thanks @jbrockmendel yeah has been out here for a while :->

followup, i think we need `.isetitem` in the api docs (and maybe a mention in the indexing.rst as well)