BUG/TST: fix several issues with slice bound checking code

BUG/TST: fix handling of slice.stop < -len, obj.iloc[:-len(obj)] should be empty

BUG/TST: fix exceptions raised by Series.iloc when slice.start > len

CLN: remove unused _check_slice_bound function and raise_on_error params
Merge pull request #6531 from immerrr/fix-out-of-bounds-slice-issues

BUG/TST: fix several issues with slice bound checking code