PyAPI: use postponed annotations to support Python 3.10

Support Python 3.10a5 or 3.9x with support explicitly enabled.

- Enable Python's postponed annotations for Blender's RNA classes
  types registered on startup.

- Using postponed annotations has implications for how they are defined,
  since they must evaluate in the modules name-space instead of the
  classes name-space. See changes to annotations in `release/scripts`.

- Use `from __future__ import annotations` at the top of the module
  to ensure the script will run with Python 3.10.

- Old logic is kept since it could be used if PEP-649 is supported.

Resolves T83626

Ref D10474

release/scripts/startup/bl_operators/__init__.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8 compliant>
+from __future__ import annotations
 
 # support reloading sub-modules
 if "bpy" in locals():

release/scripts/startup/bl_operators/add_mesh_torus.py

@@ -17,6 +17,8 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
+
 import bpy
 from bpy.types import Operator
 
@@ -156,7 +158,7 @@ class AddTorus(Operator, object_utils.AddObjectHelper):
             ('EXT_INT', "Exterior/Interior",
              "Use the exterior/interior radii for torus dimensions"),
         ),
-        update=mode_update_callback,
+        update=AddTorus.mode_update_callback,
     )
     major_radius: FloatProperty(
         name="Major Radius",

release/scripts/startup/bl_operators/anim.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 if "bpy" in locals():
     from importlib import reload

release/scripts/startup/bl_operators/assets.py

@@ -16,6 +16,9 @@
 #
 # ##### END GPL LICENSE BLOCK #####
 
+# <pep8 compliant>
+from __future__ import annotations
+
 import bpy
 
 from bpy_extras.asset_utils import (

release/scripts/startup/bl_operators/console.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 import bpy
 from bpy.types import Operator

release/scripts/startup/bl_operators/constraint.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 from bpy.types import (
     Operator,

release/scripts/startup/bl_operators/node.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 import bpy
 import nodeitems_utils
@@ -218,7 +219,7 @@ class NODE_OT_add_search(NodeAddOperator, Operator):
     node_item: EnumProperty(
         name="Node Type",
         description="Node type",
-        items=node_enum_items,
+        items=NODE_OT_add_search.node_enum_items,
     )
 
     def execute(self, context):

release/scripts/startup/bl_operators/wm.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8 compliant>
+from __future__ import annotations
 
 import bpy
 from bpy.types import (
@@ -859,9 +860,7 @@ class WM_OT_url_open_preset(Operator):
 
     type: EnumProperty(
         name="Site",
-        items=lambda self, _context: (
-            item for (item, _) in WM_OT_url_open_preset.preset_items
-        ),
+        items=WM_OT_url_open_preset._preset_items,
     )
 
     id: StringProperty(
@@ -916,6 +915,10 @@ class WM_OT_url_open_preset(Operator):
          "https://www.blender.org/about/credits/"),
     ]
 
+    @staticmethod
+    def _preset_items(_self, _context):
+        return (item for (item, _) in WM_OT_url_open_preset.preset_items)
+
     def execute(self, context):
         url = None
         type = self.type