[REG: 6.6.1 → 6.8.2] Change to singleton status of Qt

With Qt 6.8.2, the following code generates a TypeError ("Qt was a singleton at compile time, but is not a singleton anymore"):

import Qt3D.Core

Entity {
    property size textureSize: Qt.size(1024, 1024)
} 

Turning off the QML compiler avoids this TypeError. Qt 6.6.1 did not report any errors for this code.