UT[mqbblp::Domain]: introduce test driver

Add `mqbblp_domain.t.cpp` test driver:
- `test1_breathingTest` — construct / configure / reconfigure / teardown.
- `test2_concurrentConfigureAndRegisterQueue` — one thread reconfigures continuously
while the main thread registers thousands of distinct queues, exercising the exact overlap.
- `test3_reconfigureSkipsUnregisteredQueue` — deterministically (via the mock dispatcher's
enqueueOnly mode) unregisters and destroys a queue after the reconfigure is posted but
before it runs, asserting the dispatched work skips the dead queue (weak_ptr gone) and
reconfigures the survivor exactly once — proving no raw/owning reference outlives the queue.
- `test4_concurrentProcessCommandAndRegisterQueue` — one thread issues `INFO` commands
continuously while the main thread register thousands of distinct queues, exercising
the `processCommand` overlap.

Signed-off-by: Evgeny Malygin <emalygin@bloomberg.net>

Author: 678098