A couple of minor cleanups on the last commit

- Remove a redundant logger
 - Provide a getter for the ComputerCraft thread group. This allows us
   to monitor child threads within prometheus.
 - Replace a deprecated call with a fastutils alternative.

src/main/java/dan200/computercraft/core/lua/CobaltLuaMachine.java

@@ -129,7 +129,6 @@ public class CobaltLuaMachine implements ILuaMachine
                         Tracking.addValue( m_computer, TrackingField.COROUTINES_DISPOSED, 1 );
                     }
                 } );
-                ComputerCraft.log.info( "Thread pool: " + coroutines );
             } )
             .build();
 

src/main/java/dan200/computercraft/core/tracking/ComputerTracker.java

@@ -106,7 +106,7 @@ public class ComputerTracker
 
         synchronized( fields )
         {
-            return fields.get( field );
+            return fields.getLong( field );
         }
     }
 

src/main/java/dan200/computercraft/shared/util/ThreadUtils.java

@@ -21,6 +21,16 @@ public final class ThreadUtils
     {
     }
 
+    /**
+     * Get the base thread group, that all off-thread ComputerCraft activities are run on.
+     *
+     * @return The ComputerCraft group.
+     */
+    public static ThreadGroup group()
+    {
+        return baseGroup;
+    }
+
     /**
      * Construct a group under ComputerCraft's shared group
      *