Remove '__alive' from public Scheduler interface

Author: ssoelvsten

rt/src/SchedulerInterface.mts

@@ -5,8 +5,7 @@ export interface SchedulerInterface {
     // tailToTroupeFun_raw(f: any)
     // stepThread();
     resetScheduler();
-    __alive: any;
-    scheduleNewThreadAtLevel(fun: any, arg: any, pc: any, blockingTopLev: any);        
+    scheduleNewThreadAtLevel(fun: any, arg: any, pc: any, blockingTopLev: any);
     scheduleThread(theThread: any);
     resumeLoopAsync();
     blockThread(__currentThread: Thread);

rt/src/builtins/monitor.mts

@@ -14,7 +14,7 @@ export function BuiltinMonitors <TBase extends Constructor<UserRuntimeZero>> (Ba
 
             // 1. find the thread corresponding to that tid 
 
-            let t = this.runtime.__sched.__alive[tid.toString()];
+            let t = this.runtime.__sched.getThread(tid);
             // 2. update the monitor state of that thread
 
             let r = this.runtime.rt_mkuuid();