Fixing shift() for ExtensionArray
- [x] closes #23911 
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Hello @varadgunjal! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/arrays/base.py`](https://github.com/varadgunjal/pandas/blob/8766f8659f839337fc39118f78df3631c0e4e11f/pandas/core/arrays/base.py) !

 - There are no PEP8 issues in the file [`pandas/tests/extension/base/interface.py`](https://github.com/varadgunjal/pandas/blob/8766f8659f839337fc39118f78df3631c0e4e11f/pandas/tests/extension/base/interface.py) !

