Load popup contents inline before moving inside the popup

in order for global shortcuts of hidden applets to corretly work, they should have been disaplayed once, for 2 reasons:

• PlasmoidItem does a bunch of initializations only when it gets first rendered, to save (potentially a lot) of time when a lot of disabled desktops are there (disconnected screens, other activities)
• the GridView won't instantiate any delegate if isn't shown in a scene before

Only the first could be potentially worked around by adding some api to AppletQuickItem, but there is no way to force an hidden GridView to instantiate any item