refactor: moving connector label to connector view (#11738)

### Changed
Moved connector label moving logic from `default-tool` to connector view.

#### Other infrastructure changes:​​
- Gfx element view now can handles drag events
- Added `context.preventDefault()` support to bypass built-in interactions in extension
- Handle the pointer events in element view will bypass the built-in interactions automatically

> The built-in interactions include element dragging, click selection, drag-to-scale operations, etc.

blocksuite/framework/std/src/gfx/view/view.ts

@@ -26,6 +26,9 @@ export type EventsHandlerMap = {
   pointerleave: PointerEventState;
   pointermove: PointerEventState;
   pointerup: PointerEventState;
+  dragstart: PointerEventState;
+  dragmove: PointerEventState;
+  dragend: PointerEventState;
 };
 
 export type SupportedEvent = keyof EventsHandlerMap;
@@ -97,11 +100,24 @@ export class GfxElementModelView<
     return this.model.containsBound(bounds);
   }
 
+  /**
+   * Dispatches an event to the view.
+   * @param event
+   * @param evt
+   * @returns Whether the event view has any handlers for the event.
+   */
   dispatch<K extends keyof EventsHandlerMap>(
     event: K,
     evt: EventsHandlerMap[K]
   ) {
-    this._handlers.get(event)?.forEach(callback => callback(evt));
+    const handlers = this._handlers.get(event);
+
+    if (handlers?.length) {
+      handlers.forEach(callback => callback(evt));
+      return true;
+    }
+
+    return false;
   }
 
   getLineIntersections(start: IVec, end: IVec) {