Currently the lockscreen takes 5 seconds to load for me on the OnePlus 6. This MR moves the quicksettings and status bar to only load once the initial lockscreen has loaded (to avoid blocking it). This brings it down the initial load to 1 second for me.
Move from a C++ library + QML plugin to a QML plugin only for simplicity, since the homescreen switching architecture will be done from Plasma, and so use of the shell library only needs to be from QML.