Improve performance of various commands/actions

- Add chunk preloading to RegionVisitor if supplied with a suitable Extent
 - Where extents are used in masks, set EditSession as the extent as they are otherwise initialised with WorldWrapper that is very slow
 - Fixes #1073

worldedit-core/src/main/java/com/sk89q/worldedit/EditSession.java

@@ -1242,7 +1242,7 @@ public class EditSession extends PassthroughExtent implements AutoCloseable {
                 }
             }
             return true;
-        });
+        }, this);
         Operations.completeBlindly(visitor);
         return this.changes;
     }
@@ -2783,7 +2783,7 @@ public class EditSession extends PassthroughExtent implements AutoCloseable {
             } catch (EvaluationException e) {
                 throw new RuntimeException(e);
             }
-        });
+        }, this);
         Operations.completeBlindly(visitor);
         changes += visitor.getAffected();
         return changes;