Inconsistent output for optional parameters/attributes

Describe the bug

The type of an optional parameter in

:param Optional[str] bar: The bar parameter

will be output differently than that of an optional attribute:

.. attribute :: bar
   :type: Optional[str]

or when there's a type annotation on the paramter itself:

def foo(bar: Optional[str]):
   ...

How to Reproduce

The following Python sourceode:

class Test:
    """
    Test class.
    """
    def foo(self, bar: Optional[str]):
        """
        .. attribute :: bar
           :type: Optional[str]

            The bar attribute

        :param Optional[str] bar: The bar parameter.
        """
        pass

when incorporated into a Sphinx project via .. automodule:: etc. gives the following HTML output:

The type annotation Optional[str] should be displayed consistently as str | None in all three spots, instead of as Optional[str] for :param:, and str | None for .. attribute and type annotations in the function signature.

Environment Information

`sphinx-build --bug-report` gives:


Platform:              darwin; (macOS-10.16-x86_64-i386-64bit)
Python version:        3.9.13 (v3.9.13:6de2ca5339, May 17 2022, 11:23:25)
[Clang 6.0 (clang-600.0.57)])
Python implementation: CPython
Sphinx version:        7.1.0
Docutils version:      0.18.1
Jinja2 version:        3.1.2
Pygments version:      2.15.1

Sphinx extensions

No response

Additional context

No response

Start with the Python source example and reproduce it in a Sphinx project using the mentioned .. automodule:: entry point. Compare the HTML for the parameter, attribute, and function signature; the work is done when all three display Optional[str] consistently as str | None.