QLabel with embedded image using 'qrc:/' will no longer load

If an <img> tag in a QLabel uses "qrc:/" to begin the URL the image will not be loaded.

This appears to be a regression from QTBUG-60793, as prior to that commit QTextImageHandler.cpp would remove the 'qrc' from the front of these urls. _q_resolveEntryAndCreateLegacyEngine_recursive in qfilesystemengine.cpp assumes resource URLs begin with ':' so it will no longer create as QResourceFileEngine for urls starting with 'qrc'.