feat(kernel): SystemControl cap for halt, board device table + boot caps to init, RegionAddress syscall, idle loop services irqs

crates/domain/src/irq/mod.rs

@@ -30,6 +30,11 @@ impl IrqRoutingTable {
         }
     }
 
+    /// Whether `irq` is a line this table can route.
+    pub fn is_valid(&self, irq: IrqId) -> bool {
+        (irq.raw() as usize) < MAX_IRQS
+    }
+
     /// Routes `irq`, replacing any previous route. Fails for lines beyond
     /// the table.
     pub fn set(&mut self, irq: IrqId, route: IrqRoute) -> bool {