Integrate optional native KUnit suites with out-of-tree SCST modules.
A single CONFIG_SCST_KUNIT_TEST switch includes all test objects of
each owner. Declare each suite name and label once and discover source
registrations for kunit-list without a build or loaded modules.
Preserve ordinary builds without KUnit.
Start with a fixed-wire LUN regression. Centralize private visibility
and task-scoped static-stub switches, and define retained-fixture
reporting for asynchronous tests. Use current native KUnit APIs
without compatibility shims. Keep optional execution messages behind
CONFIG_SCST_KUNIT_LOG while leaving failure diagnostics unconditional.
Add Makefile/Kbuild regression checks and document the shared switch.
Keep compatibility builds free of KUnit, including inherited test
options and allmodconfig. Generate ordinary in-tree SCST patches with
private declarations but without test suites or KUnit build options.
Check this boundary and preserve kernels without an unwinder option.
