kunit: add KUNIT_INIT_TABLE to init linker section

Add KUNIT_INIT_TABLE to the INIT_DATA linker section.

Alter the KUnit macros to create init tests:
kunit_test_init_section_suites

Update lib/kunit/executor.c to run both the suites in KUNIT_TABLE and
KUNIT_INIT_TABLE.

Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Rae Moar <rmoar@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>