feat(editor): slash menu and toolbar widget extensions (#12002)

Closes: BS-3226
Closes: BS-3227
Closes: BS-3228
Closes: BS-3229

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Introduced new view extensions for remote selection, scroll anchoring, slash menu, and toolbar widgets, enhancing customization and integration capabilities.

- **Refactor**
  - Updated export paths and module structure for widget-related packages to improve modularity and accessibility.
  - Reorganized internal dependencies and removed redundant widget imports from core block packages.
  - Refactored edgeless-related widgets and components to use a standardized scope interface for improved context and state management.
  - Centralized graphics controller access and slot management through standardized context objects.

- **Chores**
  - Added and updated dependencies to streamline extension loading and workspace management.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/widgets/remote-selection/package.json

@@ -12,6 +12,7 @@
   "dependencies": {
     "@blocksuite/affine-block-surface": "workspace:*",
     "@blocksuite/affine-components": "workspace:*",
+    "@blocksuite/affine-ext-loader": "workspace:*",
     "@blocksuite/affine-model": "workspace:*",
     "@blocksuite/affine-shared": "workspace:*",
     "@blocksuite/global": "workspace:*",
@@ -26,7 +27,8 @@
   },
   "exports": {
     ".": "./src/index.ts",
-    "./effects": "./src/effects.ts"
+    "./effects": "./src/effects.ts",
+    "./view": "./src/view.ts"
   },
   "files": [
     "src",