feat(core): markdown-diff & patch apply (#12844)

## New Features
- **Markdown diff**: 
- Introduced block-level diffing for markdown content, enabling
detection of insertions, deletions, and replacements between document
versions.
  - Generate patch operations from markdown diff.
- **Patch Renderer**: Transfer patch operations to a render diff which
can be rendered into page body.
- **Patch apply**：Added functionality to apply patch operations to
documents, supporting block insertion, deletion, and content
replacement.

## Refactors
* Move `affine/shared/__tests__/utils` to
`blocksuite/affine-shared/test-utils`


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

* **New Features**
* Introduced utilities for declarative creation and testing of document
structures using template literals.
* Added new functions and types for block-level markdown diffing and
patch application.
* Provided a utility to generate structured render diffs for markdown
blocks.
* Added a unified test-utils entry point for easier access to testing
helpers.

* **Bug Fixes**
* Updated import paths in test files to use the new test-utils location.

* **Documentation**
* Improved example usage in documentation to reflect the new import
paths for test utilities.

* **Tests**
* Added comprehensive test suites for markdown diffing, patch
application, and render diff utilities.

* **Chores**
* Updated package dependencies and export maps to expose new test
utilities.
* Refactored internal test utilities organization for clarity and
maintainability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

> CLOSE AI-271 AI-272 AI-273

packages/frontend/core/package.json

@@ -19,6 +19,7 @@
     "@affine/templates": "workspace:*",
     "@affine/track": "workspace:*",
     "@blocksuite/affine": "workspace:*",
+    "@blocksuite/affine-shared": "workspace:*",
     "@blocksuite/icons": "^2.2.13",
     "@blocksuite/std": "workspace:*",
     "@dotlottie/player-component": "^2.7.12",
@@ -89,6 +90,7 @@
     "zod": "^3.24.1"
   },
   "devDependencies": {
+    "@blocksuite/affine-ext-loader": "workspace:*",
     "@testing-library/dom": "^10.4.0",
     "@testing-library/react": "^16.1.0",
     "@types/animejs": "^3.1.12",