Customizing module types initialization outdated

[progsource]

Your Godot version: stable (4.x)

Issue description:

URL to the documentation page: https://docs.godotengine.org/en/stable/contributing/development/core_and_modules/custom_modules_in_cpp.html#customizing-module-types-initialization

The preregister_{module_name}_types() does not work anymore. Instead probably if (p_level == MODULE_INITIALIZATION_LEVEL_CORE) inside of the initialize_{module_name}_module() should be used.

It would be awesome to have some documentation about when to use what value from the ModuleInitializationLevel enum.
This then also could be referenced in https://docs.godotengine.org/en/stable/classes/class_gdextension.html or vice versa.