Fix sphinx-doc#9630: autosummary: Failed to build summary table if primary_domain is not 'py'

Autosummary generates reST code that uses raw `:obj:` xrefs to refer
the python objects in the summary table.  But they're fragile because
they assume the primary_domain=='py'.

This adds `:py:` prefix to these xrefs to make them robust.

Author: tk0miya

CHANGES

@@ -18,6 +18,8 @@ Bugs fixed
 
 * #9630: autodoc: Failed to build cross references if :confval:`primary_domain`
   is not 'py'
+* #9630: autosummary: Failed to build summary table if :confval:`primary_domain`
+  is not 'py'
 
 Testing
 --------

sphinx/ext/autosummary/__init__.py

@@ -444,9 +444,9 @@ def append_row(*column_texts: str) -> None:
         for name, sig, summary, real_name in items:
             qualifier = 'obj'
             if 'nosignatures' not in self.options:
-                col1 = ':%s:`%s <%s>`\\ %s' % (qualifier, name, real_name, rst.escape(sig))
+                col1 = ':py:%s:`%s <%s>`\\ %s' % (qualifier, name, real_name, rst.escape(sig))
             else:
-                col1 = ':%s:`%s <%s>`' % (qualifier, name, real_name)
+                col1 = ':py:%s:`%s <%s>`' % (qualifier, name, real_name)
             col2 = summary
             append_row(col1, col2)