Consolidate enum values for Image.fillMode and VectorImage.fillMode

Compare the following:

• https://doc.qt.io/qt-6/qml-qtquick-image.html#fillMode-prop
• https://doc.qt.io/qt-6/qml-qtquick-vectorimage-vectorimage.html#fillMode-prop

They have different names for the "no transform" mode: VectorImage.NoResize vs. Image.Pad. It would be good, from an API consistency point of view, to give them the same names (and aliases).

I also notice that Image has Tile options while VectorImage doesn't, but I presume VectorImage has a reason for omitting these?