ktest: Add test type make_min_config

ktest: Add test type make_min_config

After doing a make localyesconfig, your kernel configuration may
not be the most useful minimum configuration. Having a true minimum
config that you can use against other configs is very useful if
someone else has a config that breaks on your code. By only forcing
those configurations that are truly required to boot your machine
will give you less of a chance that one of your set configurations
will make the bug go away. This will give you a better chance to
be able to reproduce the reported bug matching the broken config.

Note, this does take some time, and may require you to run the
test over night, or perhaps over the weekend. But it also allows
you to interrupt it, and gives you the current minimum config
that was found till that time.

Note, this test automatically assumes a BUILD_TYPE of oldconfig
and its test type acts like boot.

TODO: add a test version that makes the config do more than just
      boot, like having network access.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>