This reverts the changes made in eb733982acf0992fbae822d0feb582fb07ad010f
for PY-40233.
The original problem was PyShadowingBuiltinsInspection erroneously reporting
redefining private names declared in builtins.pyi, such as _T, however,
resolving underscored names from all .pyi stubs was prohibited to fix that.
These are considered "stub-only objects" according to the typing spec
(https://typing.readthedocs.io/en/latest/guides/writing_stubs.html#stub-only-objects),
but it doesn't prohibit reusing them in other stubs and in .py files under
an `if typing.TYPE_CHECKING:` guard.
Besides, both Mypy and Pyright resolve such names imported from .pyi stubs without warnings,
so it doesn't make sense to enforce additional visibility restrictions from our side.
Also, I enabled completing such names in other .pyi stubs (but not in .py files).
Previously, in PY-38172 their completion was disabled everywhere.
GitOrigin-RevId: 8340d4dcaf732d18d481bbee824ffdddd2719d3d
Previously, we looked only for __init__.py to detect re-exported names,
ignoring __init__.pyi that could be used for the same purpose in stub
packages.
GitOrigin-RevId: 48bc58789e47d5b9fb814b99722371fdd670ee2d