Documentation generation for GDScript

- ClassDoc added to GDScript and property reflection data were extracted
from parse tree

- GDScript comments are collected from tokenizer for documentation and
applied to the ClassDoc by the GDScript compiler

- private docs were excluded (name with underscore prefix and doesn't
have any doc comments)

- default values (of non exported vars), arguments are extraced from the
parser

- Integrated with GDScript 2.0 and new enums were added.

- merge conflicts fixed

modules/visual_script/visual_script.h

@@ -342,6 +342,13 @@ public:
 	virtual void set_source_code(const String &p_code) override;
 	virtual Error reload(bool p_keep_state = false) override;
 
+#ifdef TOOLS_ENABLED
+	virtual const Vector<DocData::ClassDoc> &get_documentation() const override {
+		static Vector<DocData::ClassDoc> docs;
+		return docs;
+	}
+#endif // TOOLS_ENABLED
+
 	virtual bool is_tool() const override;
 	virtual bool is_valid() const override;