### Godot version

4.2 247c354

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

#75778 exposed `_validate_property()` to scripting. It's implemented in GDScript and C#, but not GDExtension (depends on #78634).
https://github.com/godotengine/godot/blob/247c3548d810136ffe9c1694cd76db3236efaa90/core/object/script_language_extension.h#L685-L687

Relevant discussion: https://github.com/godotengine/godot/pull/75778#discussion_r1307294940

### Steps to reproduce

1. Add GDExtension script
2. Use `_validate_property()`

### Minimal reproduction project

N/A
* Provided struct can be safely freed once the function returns.
 *
 * @param p_library A pointer the library received by the GDExtension's entry point function.
 * @param p_class_name A pointer to a StringName with the class name.
 * @param p_parent_class_name A pointer to a StringName with the parent class name.
 * @param p_extension_funcs A pointer to a GDExtensionClassCreationInfo2 struct.
 */
typedef void (*GDExtensionInterfaceClassdbRegisterExtensionClass2)(GDExtensionClassLibraryPtr p_library, GDExtensionConstStringNamePtr p_class_name, GDExtensionConstStringNamePtr p_parent_class_name, const GDExtensionClassCreationInfo2 *p_extension_funcs);
/**
 * @name classdb_register_extension_class_method
 * @since 4.1
 *
 * Registers a method on an extension class in the ClassDB.
 *
 * Provided struct can be safely freed once the function returns.
 *
 * @param p_library A pointer the library received by the GDExtension's entry point function.
 * @param p_class_name A pointer to a StringName with the class name.
 * @param p_method_info A pointer to a GDExtensionClassMethodInfo struct.
 */
typedef void (*GDExtensionInterfaceClassdbRegisterExtensionClassMethod)(GDExtensionClassLibraryPtr p_library, GDExtensionConstStringNamePtr p_class_name, const GDExtensionClassMethodInfo *p_method_info);
/**
 * @name classdb_register_extension_class_integer_constant
 * @since 4.1
 *
 * Registers an integer constant on an extension class in the ClassDB.
 *
 * @param p_library A pointer the library received by the GDExtension's entry point function.
 * @param p_class_name A pointer to a StringName with the class name.
 * @param p_enum_name A pointer to a StringName with the enum name.