init: Add some ASAN helpers

Init is special.

It starts early and does not pick up the Android ASAN options provided
on the environment.  Therefore we pull in /system/asan.options in
explicitly if it exists.  We provide sane defaults that will allow the
system to boot otherwise.

Logging is complicated because it needs to go to the kernel log.
So use sanitizer functions to install log functions.

Bug: 117879229
Test: m && m SANITIZE_TARGET=address
Test: init boots with ASAN enabled
Change-Id: I72c033a1f86ba5d6b2e4f943e7a3acd0d399c8bf