Better communicate that IOError and WindowsError are just aliases of OSError now

[sobolevn]

Bug report

While working on some Windows-related typeshed PRs, I've noticed that some places in docs are very clear about this change. For example:

.. versionchanged:: 3.3
   :exc:`IOError` used to be raised; it is now an alias of :exc:`OSError`.

It is clear that OSError is the same as IOError now.

But, there are several places where it is not clear. Example:

cpython/Doc/library/gettext.rst

Lines 165 to 170 in 92ca90b

	If no :file:`.mo` file is found, this function raises :exc:`OSError` if
	*fallback* is false (which is the default), and returns a
	:class:`NullTranslations` instance if *fallback* is true.
	.. versionchanged:: 3.3
	:exc:`IOError` used to be raised instead of :exc:`OSError`.

It might be confusing: people might think that right now OSError and IOError are different.
Let's add notes about explicit alias to several places that miss it.

Linked PRs

• gh-110497: Add note about OSError being an alias to IOError in docs #110498
• [3.11] gh-110497: Add note about OSError being an alias to IOError in docs (GH-110498) #110545
• [3.12] gh-110497: Add note about OSError being an alias to IOError in docs (GH-110498) #110546

[nanjekyejoannah]

Closing because PR is merged.