Anim: add "legacy behavior" option to Limit Rotation constraint

This adds a "Legacy Behavior" option to the Limit Rotation constraint that makes
it behave how Limit Rotation constraints did prior to
ed2408400d. Newly created constraints have this
option disabled, but versioning code enables the option on constraints from
older files to ensure that the behavior of e.g. existing rigs is not altered.

This is one part of a two-part fix for #123105. The other part is in PR
extensions/rigify#4.

Pull Request: https://projects.blender.org/blender/blender/pulls/123361

scripts/startup/bl_ui/properties_constraint.py

@@ -233,6 +233,7 @@ class ConstraintButtonsPanel:
 
         layout.prop(con, "euler_order", text="Order")
         layout.prop(con, "use_transform_limit")
+        layout.prop(con, "use_legacy_behavior")
         self.space_template(layout, con, target=False, owner=True)
 
         self.draw_influence(layout, con)