Add buttons to reorder inspector array items without dragging

[jmb462]

Describe the project you are working on

A 3D game editor using OptionButtons.

Describe the problem or limitation you are having in your project

As @markopolojorgensen explains in issue godotengine/godot#80524, array items in editor inspector can be reordered by dragging with mouse. But if the number of item is above 5, a pagination system is used. As a consequence, there is no way to move an item from a page to another via editor.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

I propose to add two buttons in order to move an item one step up or down.

If down button is used on an item at the bottom of a page, it will send it at the top of the following page.
If top button is used on an item at the top of a page, it will send it at the bottom of the previous page.

It will allow to use drag move inside a page and button move inside and across page.

The up and down button system is already used in some part of the editor (eg. autoload panel to reorder autoload scripts/scenes) so it seems to be consistent to add one here.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Here is a capture of the feature proposed :

If this enhancement will not be used often, can it be worked around with a few lines of script?

Used often if managing array items in inspector.

Is there a reason why this should be core and not an add-on in the asset library?

It's an editor inspector enhancement.