Make executeMainThreadTask a default method

- Move TaskCallback into the API and make it package private. This
   effectively means it's not an API class, just exists there for
   convenience reasons.
 - Replace any usage of TaskCallback.make with
   ILuaContext.executeMainThreadTask.
 - Some minor formatting/checkstyle changes to bring us inline with
   IntelliJ config.

src/test/java/dan200/computercraft/core/apis/ObjectWrapper.java

@@ -8,7 +8,6 @@ package dan200.computercraft.core.apis;
 import dan200.computercraft.api.lua.*;
 import dan200.computercraft.core.asm.LuaMethod;
 import dan200.computercraft.core.asm.NamedMethod;
-import dan200.computercraft.core.asm.TaskCallback;
 
 import javax.annotation.Nonnull;
 import java.util.HashMap;
@@ -65,11 +64,4 @@ public class ObjectWrapper implements ILuaContext
     {
         throw new IllegalStateException( "Method should never queue events" );
     }
-
-    @Nonnull
-    @Override
-    public MethodResult executeMainThreadTask( @Nonnull ILuaTask task ) throws LuaException
-    {
-        return TaskCallback.make( this, task );
-    }
 }

src/test/java/dan200/computercraft/core/asm/GeneratorTest.java

@@ -124,7 +124,7 @@ public class GeneratorTest
     {
         @LuaFunction
         public final void go()
-        { }
+        {}
     }
 
     public static class Basic2 extends Basic
@@ -139,14 +139,14 @@ public class GeneratorTest
     {
         @LuaFunction
         public final void go()
-        { }
+        {}
     }
 
     public static class NonInstance
     {
         @LuaFunction
         public static void go()
-        { }
+        {}
     }
 
     public static class IllegalThrows
@@ -162,42 +162,42 @@ public class GeneratorTest
     {
         @LuaFunction( { "go1", "go2" } )
         public final void go()
-        { }
+        {}
     }
 
     public static class ArgKinds
     {
         @LuaFunction
         public final void objectArg( Object arg )
-        { }
+        {}
 
         @LuaFunction
         public final void intArg( int arg )
-        { }
+        {}
 
         @LuaFunction
         public final void optIntArg( Optional<Integer> arg )
-        { }
+        {}
 
         @LuaFunction
         public final void context( ILuaContext arg )
-        { }
+        {}
 
         @LuaFunction
         public final void arguments( IArguments arg )
-        { }
+        {}
 
         @LuaFunction
         public final void unknown( IComputerAccess arg )
-        { }
+        {}
 
         @LuaFunction
         public final void illegalMap( Map<String, Integer> arg )
-        { }
+        {}
 
         @LuaFunction
         public final void optIllegalMap( Optional<Map<String, Integer>> arg )
-        { }
+        {}
     }
 
     public static class EnumMethods
@@ -219,7 +219,7 @@ public class GeneratorTest
     {
         @LuaFunction( mainThread = true )
         public final void go()
-        { }
+        {}
     }
 
     private static <T> T find( Collection<NamedMethod<T>> methods, String name )
@@ -256,12 +256,5 @@ public class GeneratorTest
         {
             return 0;
         }
-
-        @Nonnull
-        @Override
-        public MethodResult executeMainThreadTask( @Nonnull ILuaTask task ) throws LuaException
-        {
-            return TaskCallback.make( this, task );
-        }
     };
 }