illumos gate

In upstream (FreeBSD) bhyve, SVM event injection is done with the global interrupt flag (GIF) disabled, effectively blocking all interrupts while that work is performed. Since illumos-bhyve uses adaptive mutexes for data structures, rather than spinlocks, that injection logic was moved outside the section where the GIF was cleared. This opens up the possibility of event injection interrupts being missed because they were delivered after the injection logic ran, but before interrupts were disabled (so the notification would be queued until SVM entry). Just like in #13132, this logic could be split up and refactored to eliminate the possibility of missed notifications.