Add a `icon.fillMode` property to icons in QtQuick Controls 2

<svg width="512" height="256">
 <circle cx="256" cy="128" r="96" style="fill: red; stroke: black; stroke-width: 24"/>
</svg>

<svg width="256" height="512">
 <circle cx="128" cy="256" r="96" style="fill: blue; stroke: black; stroke-width: 24"/>
</svg> 

import QtQuick 2.15
import QtQuick.Controls 2.15
import QtQuick.Window 2.15

Window {
    ComboBox {
        anchors.centerIn: parent
        model: 2
        delegate: MenuItem {
            width: parent.width
            text: "Index " + modelData
            icon.source: index + ".svg"
            icon.color: "transparent"
        }
    }
}