ANDROID: cuttlefish_defconfig: enable heap and stack initialization.

This patch enables CONFIG_INIT_STACK_ALL=y and
CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y, effectively turning on stack and heap
initialization in cuttlefish kernels.

Doing so will help us mitigate information leaks and make code that
depends on uninitialized memory execute deterministically. We'll also
get coverage for the initialization features on the existing kernel
tests.

Bug: 144999193

Change-Id: I1b5914a87a235d4f416cd64d7c9a5d410da09c35
Signed-off-by: Alexander Potapenko <glider@google.com>