[GetGlobalPlacement] Issue with the scale computation

The macro return the wrong result for an object with rotation `0.45642222410108496, 0.49809724456331667, 0.5849212871934979, -0.4488262203714842`. The returned scale factor is `-1, -1, 1` but should be `1, 1, 1`. According to [this](https://math.stackexchange.com/a/3554913), the scale computation involves the eigenvalue decomposition.

I already fixed the issue for objects that are not scaled in [47dbb41](https://github.com/FreeCAD/FreeCAD-macros/commit/47dbb41e6dcb3ef678c9e479ef0248dab2fdb254). The issue subsists for scaled objects but a warning is printed.

I added a test for this.

@Jolbas do you have the capacity to have a look at this?