Add `py:type` directive and role for documenting type aliases (#11989)

Co-authored-by: Adam Turner <9087854+aa-turner@users.noreply.github.com>

tests/roots/test-domain-py/index.rst

@@ -8,3 +8,4 @@ test-domain-py
     module_option
     abbr
     canonical
+    type_alias

tests/roots/test-domain-py/module.rst

@@ -64,3 +64,6 @@ module
 
 .. py:data:: test2
     :type: typing.Literal[-2]
+
+.. py:type:: MyType1
+    :canonical: list[int | str]

tests/roots/test-domain-py/roles.rst

@@ -5,14 +5,19 @@ roles
 
 .. py:method:: top_level
 
+.. py:type:: TopLevelType
+
 * :py:class:`TopLevel`
 * :py:meth:`top_level`
+* :py:type:`TopLevelType`
 
 
 .. py:class:: NestedParentA
 
     * Link to :py:meth:`child_1`
 
+    .. py:type:: NestedTypeA
+
     .. py:method:: child_1()
 
         * Link to :py:meth:`NestedChildA.subchild_2`
@@ -46,3 +51,4 @@ roles
         * Link to :py:class:`NestedParentB`
 
 * :py:class:`NestedParentA.NestedChildA`
+* :py:type:`NestedParentA.NestedTypeA`

tests/roots/test-domain-py/type_alias.rst

@@ -0,0 +1,15 @@
+Type Alias
+==========
+
+.. py:module:: module_two
+
+   .. py:class:: SomeClass
+
+:py:type:`.MyAlias`
+:any:`MyAlias`
+:any:`module_one.MyAlias`
+
+.. py:module:: module_one
+
+   .. py:type:: MyAlias
+      :canonical: list[int | module_two.SomeClass]