Type Series

[MarcoGorelli]

closes #1444

• Closes #xxxx (Replace xxxx with the Github issue number)
• Tests added: Please use assert_type() to assert the type of any return value

[cmp0xff]

Just a kind reminder: please remove

"*series.pyi" = [
  # TODO: remove when pandas-dev/pandas-stubs#1444 is resolved
  "ANN001", "ANN201", "ANN204", "ANN206",
]

from pyproject.toml when this is ready. Thanks.

[cmp0xff]

One question.

[cmp0xff]

There is room to improve. Examples:

• __getitem__ and __setitem__ are duplicated. I think we can make @type_check_only classes to deduplicate.
• pd.Series([1, 2]).iloc[pd.Series([1])] seems to work, so idx in __setitem__ can also be Series, it seems to me
• Index | Series may be worthy to combine into IndexOpsMixin

Overall, the PR does what it should - adding types to Series. I'll give green light. The new ideas can be addressed in a separate PR with new tests. Thank you @MarcoGorelli !