Make code role highlighting consistent with code-block directive

Fixes https://github.com/sphinx-doc/sphinx/issues/5157

This is factored out of the sphinx-immaterial theme:
1ef121a612/sphinx_immaterial/inlinesyntaxhighlight.py (L1)

See also:
https://github.com/sphinx-doc/sphinx/pull/6916

tests/roots/test-reST-code-role/index.rst

@@ -0,0 +1,9 @@
+.. role:: python(code)
+   :language: python
+   :class: highlight
+
+Inline :python:`def foo(1 + 2 + None + "abc"): pass` code block
+
+.. code-block:: python
+
+   def foo(1 + 2 + None + "abc"): pass