Add protected broadcasts for model loaded/unloaded events.

Removing configurable broadcasts to use constants instead. Android requires all broadcasts sent from system-process to be `protected`. So, this CL replaces config based broadcast names to defined protected-broadcasts.

Bug: 363926129
Flag: EXEMPT bugfix
Change-Id: Iad56bc37427337e11a65f0afce4291b8bc749490
3 files changed