`Series.loc`, `Series.iloc`, `DataFrame.loc` and `DataFrame.iloc` not accepting singular slice arguments for `__setitem__()` (and possibly `__getitem()`)

[randolf-scholz]

Describe the bug

To perform complicated in-place operations, one can do df.loc[:] = ..., to simply assign the updated array. This is currently unsupported by pandas-stubs.

To Reproduce

from pandas import DataFrame, Series

foo = Series([1, 2, 3])
foo.loc[:] = 1 + foo  # [call-overload]

bar = DataFrame([1, 2, 3])
bar.loc[:] = 1 + bar  # [call-overload]

Please complete the following information:

• pandas 1.5.3
• pandas-stubs 1.5.3.230304

[Dr-Irv]

Have to add singluar slice arguments to __getitem__() and __setitem__() in the right places for dataframe.pyi in _LocIndexerFrame and _ILocIndexerFrame and series.pyi in _LocIndexerSeries and ILocIndexerSeries.

Needs a fair bit of tests to make sure this is done correctly.