BUG: fix setitem with enlargment with pyarrow Scalar
Potentially closes #52235

This updates `lib.is_scalar` to recognize pyarrow.Scalar objects. 

Further, it updates a very specific code path for setitem with enlargement with a scalar to preserve the arrow extension dtype (#52235). There are many other places where specific handling would need to be added for pyarrow Scalars for generally supporting them.

- [ ] [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.

In #27462 you suggested a method on the EADtype/EA to check for a recognized scalar (might be similar to _recognized_scalars on our datetimelike EAs).  I think this might be the right approach long-term. (which isn't mutually exclusive with this PR short term)
 I went down a rabbit-hole looking at issues regarding is_scalar, have a half-written Deep Dive post about it.  For the time being I think we should hold off on updating is_scalar since it is public, do a targeted fix in the indexing code. This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. Looks like this PR has gone stale. Closing to clear the queue but feel free to reopen when you have time