Exposes get_rid() function for scripting.
Adds configuration warning when obstacle is used with not intended static body parent.
(cherry picked from commit 001d89223f1377717d2b3d5ec453ff8dd3604182)
Fixes NavigationObstacle2D/3D reporting a 'get_global_transform: Condition "!is_inside_tree()" error when estimating the agent radius.
The collisionshapes that are lower in the SceneTree order than the obstacle node are not loaded in the SceneTree yet so the global_transform function fails.
Also adds warning message when this happens.
(cherry picked from commit cc707412e909f117ad53ebe53e19bad43acf086a)
