ENH: Add use_nullable_dtypes in csv internals
- [x] xref #36712 (Replace xxxx with the Github issue number)
- [x] [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
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] 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.

This adds the required casting logic for extension array dtypes. Want to get this done as a first step before adding a public option to read_csv. The unit tests can be used as a guideline for the required behaviour.

This always casts to ea dtypes, even when no missing values are present. From a users perspective this makes the most sense imo. You don't want to do a follow up operation and end up with float in a pipeline, when you set nullable dtypes (reindexing, enlargement in indexing ops, ...). That said, if there are concerns about this, we could also do something like

``use_nullable_dtypes=False | always | when necessary``

cc @jorisvandenbossche 

Thanks @phofl 