stasis.c: Fix deadlock in stasis_topic_pool_get_topic during module load

stasis.c: Fix deadlock in stasis_topic_pool_get_topic during module load

stasis.c: Fix deadlock in stasis_topic_pool_get_topic during module load.

Deadlock occurs when res_manager_devicestate loads concurrently with
device state operations due to lock ordering violation:

Thread 1: Holds pool lock → needs topic lock (in stasis_forward_all)
Thread 2: Holds topic lock → needs pool lock (in stasis_topic_pool_get_topic)

Fix: Release pool lock before calling stasis_topic_create() and
stasis_forward_all(). Re-acquire only for insertion with race check.

Preserves borrowed reference semantics while breaking the deadlock cycle.

Fixes: #1611