Support TabBar drag and drop

[ModuleCode]

Describe the project you are working on

I am using Godot to develop a software and want to achieve a web-like effect, but I found that the Godot editor interface is not very easy to use. I have to say that it is indeed much better than the previous version, but there are still problems with inconvenience in use. I think Tabbar should be able to be dragged anywhere, such as the menu bar below, instead of specifying just a few locations where it can be dragged.

Describe the problem or limitation you are having in your project

When using the Godot editor, it is inconvenient to operate but the Tabbar cannot be dragged to the bottom.

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

Drag any Tabbar below or drag the button below to other places.I don’t know if the bottom is a button or a tabbar, but I think they should be unified as follows. Godot needs to strengthen the UI of the editor.You can refer to Unity or UE

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

Uploading QQ2024427-31044.mp4…

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

NO There are indeed such scripts at present, but I still prefer to make this a core, because this method is still not convenient enough.

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

Yes Honestly, Godot needs a UI overhaul

[KoBeWi]

The video didn't upload.
Also this might be duplicate of #1508

[ModuleCode]

Uploading QQ2024427-31044.mp4…

The video didn't upload. 视频没有上传。 Also this might be duplicate of #1508 此外，这可能与 #1508 重复

Does Godot plan to redesign the GUI in future major versions, such as 5.x?

[KoBeWi]

Uploading QQ2024427-31044.mp4…

You need to wait until it finished uploading.

Does Godot plan to redesign the GUI in future major versions, such as 5.x?

As of now, no major redesign is planned.