setElementParent on GUI elements is slightly broken

[patrikjuvonen]

Describe the bug

• It does not seem to be possible to set the parent of a GUI element to guiRoot. Also tested on root, resourceRoot and getResourceDynamicElementRoot(resource).
• It does not seem to reset the position relative to the new parent when set (from window to another, for example). Repositioning does not reload the position.

To reproduce

1. Create a GUI element and optionally another GUI element as the parent.
2. setElementParent(guiElement, guiRoot) -> doesn't do anything
3. setElementParent(guiElement, guiSecondWindow) -> sets, but doesn't reposition relative to the new parent

Expected behavior
Set parent as requested and reset position relative to the new parent.

MTA Client:
Multi Theft Auto v1.5.5-release-13968

Additional context

• Discovered by Equis#9283 on Discord. Thank you.
• Related forum topic from 2012: https://forum.mtasa.com/topic/40855-setting-parent-element-for-gui/
• I'm carrying this information forward here from Equis, so I haven't yet personally tested this issue. If someone has a working solution, let's hear it.

[Lpsd]

Will be resolved by #1459 along with other non backwards-compatible changes.

Due to this apparently not repositioning elements it could break some existing GUIs when fixed.