Since output can be cumstomized, so slightly change the output format,
so that twister can parse the output and collect the passrate correctly.
Signed-off-by: Guo Lixin <lixinx.guo@intel.com>
A Kconfig boolean is added to allow users to provide their own
output strings when running tests via ztest.
This allows changing e.g. the PASS/FAIL/SKIPPED strings,
add counters, change separators, and similar.
A test using the feature and relevant documentation is added.
Signed-off-by: Torstein Grindvik <torstein.grindvik@nordicsemi.no>