Anim: Action bake custom properties

Add custom properties to Action Bake.

objects will bake all animatable custom properties. Armatures will bake all bone custom properties,
as well as object (armature) custom properties.

Pull Request: https://projects.blender.org/blender/blender/pulls/113208

scripts/startup/bl_operators/anim.py

@@ -259,8 +259,9 @@ class NLA_OT_bake(Operator):
             ('ROTATION', "Rotation", "Bake rotation channels"),
             ('SCALE', "Scale", "Bake scale channels"),
             ('BBONE', "B-Bone", "Bake B-Bone channels"),
+            ('PROPS', "Custom Properties", "Bake custom properties")
         ),
-        default={'LOCATION', 'ROTATION', 'SCALE', 'BBONE'},
+        default={'LOCATION', 'ROTATION', 'SCALE', 'BBONE', 'PROPS'},
     )
 
     def execute(self, context):
@@ -278,6 +279,7 @@ class NLA_OT_bake(Operator):
             do_rotation='ROTATION' in self.channel_types,
             do_scale='SCALE' in self.channel_types,
             do_bbone='BBONE' in self.channel_types,
+            do_custom_props='PROPS' in self.channel_types
         )
 
         if bake_options.do_pose and self.only_selected: