BACKPORT: security: Create "kernel hardening" config area

Right now kernel hardening options are scattered around various Kconfig
files. This can be a central place to collect these kinds of options
going forward. This is initially populated with the memory initialization
options from the gcc-plugins.

The Android backport only adds INIT_STACK_NONE, as GCC plugins are
unavailable in the Android 4.14 tree.

Change-Id: I55d317a1b90a980cb9eb79645e0661881b81b335
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
(cherry picked from commit 9f671e58)
Bug: 133428616
Signed-off-by: Alexander Potapenko <glider@google.com>