Clarify that physics does not run in editor; only a few physics calls work (keywords: tool, physics, editor, raycast)

**Your Godot version:**
4.3
**Issue description:**
The need to document how physics is off in the editor by default, with a subset of operations exposed in an editor-specific way (for tool scripts and plugins) has been mentioned in several issues, but I didn't see any issues in the docs repo:
[intersect_shape not working with Area3D in tool](https://github.com/godotengine/godot/issues/87429)
[EditorPlugin intersect_ray fails on GridMap](https://github.com/godotengine/godot/issues/82912)
[CollisionShape3D not working properly as a tool](https://github.com/godotengine/godot/issues/74789)
Some discussion in this [proposal](https://github.com/godotengine/godot-proposals/issues/8963)
A suggestion for new docs text is here: https://github.com/godotengine/godot/issues/87429#issuecomment-1916081095

I did a quick skim of the issues and closed PRs for "editor physics", "raycast tool", and variations and did not see an existing issue for this.

Unsure what the best place to document this is. Probably in the tool script and/or editor plugin tutorials. Some class reference may want to clarify that it's not available in the editor, though this may get redundant fast.

The linked issues contain a good deal of explanation of the current behavior.

**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/stable/tutorials/plugins/running_code_in_the_editor.html
https://docs.godotengine.org/en/stable/classes/class_raycast2d.html