feat(core): enable new all docs by default (#12404)

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

- **Refactor**
  - Simplified the user interface by always displaying the new All Pages view, removing the feature flag and old page version.
  - Updated selection interactions to use shift+click on document items instead of checkboxes.
  - Centralized drag-and-drop functionality in document list items and simplified drag handle behavior.
  - Generalized new page button component to accept standard HTML attributes.
  - Changed test ID attributes on new page buttons and list headers to use standard `data-testid`.

- **Bug Fixes**
  - Added stable test identifiers to new page buttons, document list items, menu items, and operation buttons for improved test reliability.
  - Enabled external drag-and-drop support on the trash button.

- **Tests**
  - Streamlined and updated end-to-end tests to match the new selection flow and UI changes, removing outdated or redundant test cases.
  - Simplified utility functions and wait conditions in test helpers for better accuracy and maintainability.
  - Updated selectors in tests to reflect new document item identifiers and centralized page element retrieval using utility functions.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/modules/feature-flag/constant.ts

@@ -311,13 +311,6 @@ export const AFFINE_FLAGS = {
     configurable: false,
     defaultState: isCanaryBuild,
   },
-  enable_new_all_docs_page: {
-    category: 'affine',
-    displayName: 'Enable New All Docs Page',
-    description: 'Use new all docs page',
-    configurable: isCanaryBuild,
-    defaultState: false,
-  },
   enable_cloud_indexer: {
     category: 'affine',
     displayName: 'Enable Cloud Indexer',