Add a "full" build config.

While the generic config is limited by its need to be inherited
by various configurations, the full config can afford some extra
settings by virtue of being essentially a "leaf" config (though
obviously it can be conbined with hardware-specific configurations
to run on specific devices).

Bug: 2533998
Change-Id: Ia95f0ce5305ada4ae6cdf69911fa9a0eeabf0900