REF/TST: Add more pytest idiom to indexing/multiindex/test_iloc.py
- [ n/a] xref #24040
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ n/a] whatsnew entry

in this PR:

- unskip `test_iloc_getitem_multiindex2`. difference in series name resolved. some tests were duplicated in `test_iloc_getitem_multiindex` 
- `.ix` removed. this was only used to generate expected values. this module is to test `.loc` functionality only. integer indexing on the numpy array used to create dataframe used instead. 
- class removed
- some renaming of variables
- and splitting and paramatrizing.