Expose built-in EditorProperty classes to GDScript so they can be extended

[tx350z]

I'd like to see the built-in EditorProperty classes (e.g. EditorPropertyText) exposed to GDScript. This will make creating custom EditorInspectorPlugins much simpler.

EditorPropertyText applies changes to the exported property with every key press. This can be problematic when the property has a setter that has side-affecting logic.

For example, in my project there is an exported string property that includes a setter that manipulates files based on the string property value. Having the changes applied with every key press creates race conditions. It's pure chaos. To solve this I created a custom EditorProperty that applies changes only when the LineEdit loses focus. Sadly it does not have all the features of EditorPropertyText. Being able to extend EditorPropertyText would be best solution.