autodoc_type_aliases does not effect to variables and attributes

[tk0miya]

Describe the bug
autodoc_type_aliases does not effect to variables and attributes

To Reproduce

# example.py
from __future__ import annotations


#: blah blah blah
var: String


class MyString:
    "mystring"

    #: blah blah blah
    var: String

# index.rst
.. automodule:: example
   :members:
   :undoc-members:

# conf.py
autodoc_type_aliases = {
    'String': 'example.MyString'
}

Expected behavior
autodoc_type_aliases should be applied to example.var and example.MyString.var.

Your project
N/A

Screenshots
N/A

Environment info

• OS: Mac
• Python version: 3.9.0
• Sphinx version: HEAD of 3.x branch
• Sphinx extensions: sphinx.ext.autodoc
• Extra tools: Nothing

Additional context
N/A