[Problem] UI for copying objects is unclear

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Problem description


The "Use Original Selections" button is very unclear. It's location suggests it's some sort of option for the window itself like the two checkboxes beside it. At first I thought it served something like a "reset selections to default" within the window, that is to say, recheck every dependency as that's the default, when it's actually a copy like clicking OK just without also copying anything selected on this window.

Additionally, the text at the top describing the function of the window is a bit unclear to me. I think changing "Please select which objects to export" should be changed to "Please select which objects to copy.", since describing the selections here as being exported instead of copied makes it sound like something other than copying might be happening.

My suggestion is to move the "Use Original Selections" button over to the right hand side next to the OK button, and to change the text on it and/or the OK button to more clearly reflect what they do.

So something like this:

### Full version info

```shell
[code]
OS: Windows 10 build 19045
Word size of FreeCAD: 64-bit
Version: 0.21.0.33668 +7 (Git)
Build type: Release
Branch: (HEAD detached at 0.21)
Hash: 41b058e2087de60dc8fef3d3e68c7d0129e13abf
Python 3.8.10, Qt 5.15.2, Coin 4.0.1, Vtk 8.2.0, OCC 7.6.3
Locale: English/United States (en_US)
Installed mods:
* Assembly4 0.50.2
* Freecad-Built-in-themes-beta 1.2.2
[/code]
```

### Subproject(s) affected?

Core

### Anything else?

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct