Make sure LSC's spinner shows up duing profile regeneration on boot

Currently, if AppArmor profiles for Clicks have to be generated, it will be generated in the early boot stage (before sysinit.target). If a device have a large number of apps installed, this can hold up boot for a significant amount of time. And because this is before LightDM/lomiri-system-compositor runs, users can perceive this as the device being hang.

Ideally we should be able to generate profiles in background, however we currently don't have a mechanism to block app launch until app's profile is generated or to request profile generation on demand. So, for now, we could make sure we don't actually block LightDM from starting, but then block the startup of Lomiri using a Systemd user unit which monitor click-apparmor.service system unit. The end result is there will be Ubuntu Touch logo showing up while profile generation is still running in background.

A bonus is if the spinner can show a message saying that something is currently in process.