[BUG]: Groupy and Resample miscalculated aggregation
- [x] closes #27343
- [x] closes #33548
- [x] closes #35275
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

I think I found a solution for this issue. We used `obj.index` to get the Index values. In case of resample `obj.index` had the original index. This index was not necessarily a RangeIndex of course -> resulted in a IndexError. In case of a RangeIndex the object `self._grouper` may have been resorted -> Wrong elements were selected. The object `self.obj` stored the original DataFrame, but already sorted in the first go around (is overwritten later). I stored the mapping from original index to a new synthetic RangeIndex (sorted after the grouping column). This allows us to replace the Index of obj in a way, that the take function works.
