### 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 r_dest A pointer to a Variant to hold the newly created String.
 * @param p_contents A pointer to a UTF-32 encoded C string (null terminated).
 */
typedef void (*GDExtensionInterfaceStringNewWithUtf32Chars)(GDExtensionUninitializedStringPtr r_dest, const char32_t *p_contents);
/**
 * @name string_new_with_wide_chars
 * @since 4.1
 *
 * Creates a String from a wide C string.
 *
 * @param r_dest A pointer to a Variant to hold the newly created String.
 * @param p_contents A pointer to a wide C string (null terminated).
 */
typedef void (*GDExtensionInterfaceStringNewWithWideChars)(GDExtensionUninitializedStringPtr r_dest, const wchar_t *p_contents);
/**
 * @name string_new_with_latin1_chars_and_len
 * @since 4.1
 *
 * Creates a String from a Latin-1 encoded C string with the given length.
 *
 * @param r_dest A pointer to a Variant to hold the newly created String.
 * @param p_contents A pointer to a Latin-1 encoded C string.
 * @param p_size The number of characters.
 */
typedef void (*GDExtensionInterfaceStringNewWithLatin1CharsAndLen)(GDExtensionUninitializedStringPtr r_dest, const char *p_contents, GDExtensionInt p_size);
/**
 * @name string_new_with_utf8_chars_and_len
 * @since 4.1
 *
 * Creates a String from a UTF-8 encoded C string with the given length.