[Threading] Implement priority boost on wake

When a thread wakes from a kernel wait, the Xenon scheduler boosts its
effective priority by the increment passed to the signaling call
(KeSetEvent, KeReleaseSemaphore, KeReleaseMutant). The boost is clamped
to the per-thread max_dynamic_priority cap, respects the guest
boost_disabled flag, and is drained on the next quantum expiry.
Guest KTHREAD priority fields are now initialized from parent process
defaults, and the previously unknown fields involved have been renamed
to match their identified purpose.

src/xenia/kernel/xevent.cc

@@ -58,11 +58,13 @@ void XEvent::InitializeNative(void* native_ptr, X_DISPATCH_HEADER* header) {
 }
 
 int32_t XEvent::Set(uint32_t priority_increment, bool wait) {
+  set_priority_increment(priority_increment);
   event_->Set();
   return 1;
 }
 
 int32_t XEvent::Pulse(uint32_t priority_increment, bool wait) {
+  set_priority_increment(priority_increment);
   event_->Pulse();
   return 1;
 }