core: Put Python version as a project requirement so it is considered by ruff (#26608)

Ruff doesn't know about the python version in
`[tool.poetry.dependencies]`. It can get it from
`project.requires-python`.

Notes:
* poetry seems to have issues getting the python constraints from
`requires-python` and using `python` in per dependency constraints. So I
had to duplicate the info. I will open an issue on poetry.
* `inspect.isclass()` doesn't work correctly with `GenericAlias`
(`list[...]`, `dict[..., ...]`) on Python <3.11 so I added some `not
isinstance(type, GenericAlias)` checks:

Python 3.11
```pycon
>>> import inspect
>>> inspect.isclass(list)
True
>>> inspect.isclass(list[str])
False
```

Python 3.9
```pycon
>>> import inspect
>>> inspect.isclass(list)
True
>>> inspect.isclass(list[str])
True
```

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

libs/core/langchain_core/documents/base.py

@@ -2,9 +2,10 @@ from __future__ import annotations
 
 import contextlib
 import mimetypes
+from collections.abc import Generator
 from io import BufferedReader, BytesIO
 from pathlib import PurePath
-from typing import Any, Generator, Literal, Optional, Union, cast
+from typing import Any, Literal, Optional, Union, cast
 
 from pydantic import ConfigDict, Field, field_validator, model_validator
 

libs/core/langchain_core/documents/compressor.py

@@ -1,7 +1,8 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
-from typing import Optional, Sequence
+from collections.abc import Sequence
+from typing import Optional
 
 from pydantic import BaseModel
 

libs/core/langchain_core/documents/transformers.py

@@ -1,7 +1,8 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
-from typing import TYPE_CHECKING, Any, Sequence
+from collections.abc import Sequence
+from typing import TYPE_CHECKING, Any
 
 from langchain_core.runnables.config import run_in_executor