Remove TestData in series tests indexing
Part of #22550

* Replaced test_data fixture in `pandas/tests/series/indexing/` with more granular fixtures
* Removed pandas/tests/series/indexing/conftest.py as the test_data fixture is not needed anymore
* Removed pandas/tests/series/common.py as TestData isn't used anymore

- [x] closes #22550
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

