Inconsistent picking with different editor themes

[adriengivry]

Description
Changing editor themes slightly changes the scene view margins/padding, resulting in slightly offset picking (for instance, it makes it hard to select a gizmo).

The calculation should take into account any padding in the panel.

Overload/Sources/Overload/OvEditor/src/OvEditor/Panels/SceneView.cpp

Line 236 in 8ecae34

OvEditor::Rendering::PickingRenderPass::PickingResult OvEditor::Panels::SceneView::GetPickingResult()

To Reproduce
Steps to reproduce the behavior:

1. Open the editor
2. Select ImGui Classic editor theme
3. Select an actor
4. Move the mouse cursor over the gizmo
5. Notice that the picking area is offset

Expected behavior
Picking should be consistent across all themes.

Screenshots

OvEditor_yD54SRukbW.mp4