### 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
* @param p_script A pointer to a Script.
 * @param p_owner A pointer to an Object.
 *
 * @return A pointer to a PlaceHolderScriptInstance object.
 */
typedef GDExtensionScriptInstancePtr (*GDExtensionInterfacePlaceHolderScriptInstanceCreate)(GDExtensionObjectPtr p_language, GDExtensionObjectPtr p_script, GDExtensionObjectPtr p_owner);
/**
 * @name placeholder_script_instance_update
 * @since 4.2
 *
 * Updates a placeholder script instance with the given properties and values.
 *
 * The passed in placeholder must be an instance of PlaceHolderScriptInstance
 * such as the one returned by placeholder_script_instance_create().
 *
 * @param p_placeholder A pointer to a PlaceHolderScriptInstance.
 * @param p_properties A pointer to an Array of Dictionary representing PropertyInfo.
 * @param p_values A pointer to a Dictionary mapping StringName to Variant values.
 */
typedef void (*GDExtensionInterfacePlaceHolderScriptInstanceUpdate)(GDExtensionScriptInstancePtr p_placeholder, GDExtensionConstTypePtr p_properties, GDExtensionConstTypePtr p_values);
/**
 * @name object_get_script_instance
 * @since 4.2
 *
 * Get the script instance data attached to this object.
 *
 * @param p_object A pointer to the Object.
 * @param p_language A pointer to the language expected for this script instance.
 *
 * @return A GDExtensionScriptInstanceDataPtr that was attached to this object as part of script_instance_create.