Ensure apps cannot prevent uncaught exceptions being logged.

Let RuntimeInit use an UncaughtExceptionPreHandler to log an exception
rather than relying on UncaughtHandler, which apps can replace. This
makes it easier to diagnose application death, especially during app
compatibility testing for a new version of Android.

Test: Verified manually, with the help of a small sample app (not
checked in), that stacktraces for RuntimeExceptions thrown on main
or background threads are logged even when the app set a default
UncaughtExceptionHandler that swallows the exception with no action.

Note that such an inappropriate UncaughtExceptionHandler will still
cause threads to die without the app being killed, which it should be.
In an exception then happens on the main thread, the app will freeze
until the ANR dialog kicks in after a few seconds. I have manually
verified that this behavior is unchanged from before this CL.

No new integration tests are included because the default system
behavior has not changed.

Bug: 29624607
Change-Id: Ie87377b0bcadc3ba4083a8ab1bedb8f3dd95a4bd