Add a custom status bar

[AlstonLin]

Right now, the lock screen works by overlaying everything on top of the screen using WindowManager. Unfortunately, this means that the status bar must either be

1. Not included in the overlay, which means that the background cannot be applied to the status bar and there's some consistently wierd UI

2. Use the current configuration that will put the background behind it and then show the status bar on top. This means that it will work as long as the active app has their status bar set to transparent. This breaks if an app sets an explicit opaque background (eg. Chrome). This leads to unconsistently wierd UI

3. Draw on top of the status bar and add a custom status bar that we make ourselves. This is the most work but what other lock screens do

We should move from 2) to 3)

See LockUtils#lock