Add buttons to reorder inspector array items without dragging

[jmb462]

Closes godotengine/godot-proposals#7495
Fix #80524

Issue fix

As @markopolojorgensen explains in issue #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.

Fix proposal / feature enhancement

This PR implements the proposal godotengine/godot-proposals#7495 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 reoreder autoload script/scenes) so it seems to be consistent to add one here.

Preview

[Calinou]

Tested locally (rebased on top of master 6758a7f), it works as expected. Code looks good to me at a glance.

There are some caveats though:

• This is only available for built-in arrays, not exported array properties (or exported dictionary properties) as these use a different editor.
• There's a noticeable delay after releasing the mouse button, even in a small array of 5 items. This is likely because properties aren't force-updated after the event is handled, so it's relying on editor polling to update (which occurs every 0.2 seconds by default). Watch the video at 0.5× speed by right-clicking it:

simplescreenrecorder-2023-08-25_00.55.26.mp4

If you change the Docks > Property Editor > Auto Refresh Interval editor setting, the delay will change accordingly. It would be good to figure out whether this can be improved (without changing this default setting, as it's kept at 0.2 to reduce CPU utilization).

[KoBeWi]

Down button doesn't work.

godot.windows.editor.dev.x86_64_ll9msRhyXI.mp4

[jmb462]

@KoBeWi Fixed. I've missed that some classes use a specific function call to reorder items. (as TileMap and TileSet)

@Calinou For the delay, it seems to apply both with new buttons and with drag/drop reorder. Strangely, changing the auto refresh interval doesn't affect this delay for me (even if set to a very high or low value).

For the exported array / dict, the display is more compact and I don't know where to place new buttons without overloading the look. :(

Edit : the drag management is totaly different with exported arrays and allow to change page while dragging. Maybe we should just do the same for others arrays.

[KoBeWi]

EditorInspectorArray is for arrays of grouped properties, EditorPropertyArray is for arrays of values. They serve a bit different purposes and the latter is much more compact as a result and arrows aren't really feasible to add there.

Edit : the drag management is totaly different with exported arrays and allow to change page while dragging. Maybe we should just do the same for others arrays.

Makes sense, doesn't need to be done in this PR.

[akien-mga]

Thanks!