Rightclick context menu generation uses screen offset instead of window offset.

[Anutrix]

Alternative Title: Rightclick context menu generation uses the active window's parent's window offset instead of active window offset.

Godot version:
Latest master 46f1d4f

OS/device including version:
Windows 10 1909

Issue description:
Rightclick context menu generation uses screen offset instead of window offset.
Thus, even making context menu outside window depending on the position.

Steps to reproduce:

1. Move window anywhere accept top left default position.
2. Right-click any right-clickable thing.
3. It will be generated at the same XY offset that it should have from screen's top-left(actual) instead of window's top-left(expected).
   

Update: Another way to reproduce this is to right-click anything in the file dialogue e.g,

1. Click any node.
2. In the inspector, click the Load button for the Material property.
3. Move this EditorFileDialog to any position other than the default position.
4. Right-click anything.
5. This time it will use the main window's offset instead of the EditorFileDialog's offset.

Minimal reproduction project:
Any project.

[bruvzg]

Should be fixed by #37506

[Anutrix]

Should be fixed by #37506

Confirmed that #37506 indeed fixes this issue.
Update: Confirmed that it fixes the 2nd issue too.

[Anutrix]

Don't know which commit fixed this but I can no longer reproduce this. If someone can confirm I'll close this issue. I tested with 0f1da72.
I couldn't reproduce in the same way as earlier though. I added another way to reproduce it in the first comment.