[Python] Generated type stubs don't work #9224

Given a very simple FlatBuffer definition:

table Foo {
    bar: string;
    baz: int64;
}

root_type Foo;

The generated type stubs (flatc --python --python-typing foo.fbs) include an incorrect alias to uoffset:

from __future__ import annotations

import flatbuffers
import numpy as np

import typing

uoffset: typing.TypeAlias = flatbuffers.number_types.UOffsetTFlags.py_type

1. The corresponding Foo.py file does not define an uoffset alias.

   >>> from Foo import uoffset
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
       from Foo import uoffset
   ImportError: cannot import name 'uoffset' from 'Foo' (/.../Foo.py)

2. flatbuffers.number_types is not accessible with a simple import flatbuffers, as flatbuffers/__init__.py doesn't re-export number_types. An explicit import flatbuffers.number_types is needed.
3. The stub adds an unconditional import numpy as np, which breaks type checking when numpy is not installed.

Tested with Python 3.14.7, Pyright 1.1.411 and flatbuffers/flatc 25.12.19.