Introduce "make debugconfig"

[Qian Cai]

Hi there, some general debugging features like kmemleak, KASAN, lockdep,

UBSAN etc help fix many viruses like a microscope. On the other hand, those
 features are scatter around and mixed up with more situational debugging
 options making them difficult to consume properly.



Since I have been deal with those options on a daily basis for the last

a few years and accumulated the knowledge of their pros and cons, I am

thinking about to create an initial "make debugconfig" target, so that
it could amplify the general debugging/testing efforts and help
establish sensitive default values for those options across the broad.


The idea is to have a debugconfig inside kernel/configs/ and update
scripts/kconfig/Makefile and Documentation/admin-guide/README.rst
accordingly. I am still trying to figure out a few implementation
details like how to convert an existing .config to debugconfig, but want
to gather some feedback before I dive in too deep.