Frameworks/base: Use Log.printlns in RuntimeInit

Make printlns in Log public-@hide so it can be used.

Print uncaught exceptions that will terminate the process in
RuntimeInit using printlns, so that long exception traces are not
being truncated.

Bug: 27245306
Change-Id: Ib24635f0ebdd80bd125e367302cab6a78e6a210a