Add "validate_property" virtual func

- Change back privacy of StringName::from_opaque method.
- Formatting fixes.

Author: Yarwin

Diff for: godot-core/src/builtin/string/string_name.rs

@@ -56,7 +56,7 @@ pub struct StringName {
 }
 
 impl StringName {
-    pub(crate) fn from_opaque(opaque: sys::types::OpaqueStringName) -> Self {
+    fn from_opaque(opaque: sys::types::OpaqueStringName) -> Self {
         Self { opaque }
     }
 

Diff for: godot-core/src/meta/property_info.rs

@@ -195,6 +195,7 @@ impl PropertyInfo {
             let _hint_string = GString::from_owned_string_sys(info.hint_string);
         }
     }
+
     /// Moves its values into given `GDExtensionPropertyInfo`, dropping previous values if necessary.
     ///
     /// # Safety