Dialog's accepted() signal emitted before closed() when using non-zero-duration transitions

https://doc.qt.io/qt-5/qml-qtquick-controls2-dialog.html#accept-method says:

Closes the dialog and emits the accepted() signal.

When running this code

import QtQuick 2.12
import QtQuick.Controls 2.12

ApplicationWindow {
    width: 400
    height: 400
    visible: true

    Dialog {
        standardButtons: Dialog.Ok | Dialog.Cancel
        visible: true
        onAccepted: print("accepted")
        onClosed: print("closed")
    }
}

with the Material style (which has transitions for Dialog), the output is:

qml: accepted
qml: closed

When run with the Default style (which has no transitions for Dialog), the output is:

qml: closed
qml: accepted

Besides contradicting the documentation, the concrete problem with this is that it breaks code like this:

    onAccepted: project.modifyAnimation(animationIndex) // oops, animationIndex is -1

    onClosed: {
        animationIndex = -1
        animation = null
        acceptOnNextModify = false
    }

This worked in my application (which uses the Material style) but failed in my tests, where I use the Default style to speed things up.

I think we should fix this by changing the behaviour, and always emit accepted (and rejected) before closed, since they are emitted synchronously.