BUG: fix memory_usage method with deep of StringArray
- [ ] closes #33963
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

@kotamatsuoka thanks a lot for working on this! thanks @kotamatsuoka 

as a followup can you add tests for each EA that we have. note that it *is* possible for memory usage under deep=True to be equal to deep=False (for some implementations).