fix(core): ai replace selection (#11875)

### TL;DR

* Fix the issue of inaccurate content replacement in AI Replace Selection
* Optimize unit Tests utils

### What Changed
1. Fixed the issue of inaccurate content replacement in AI Replace Selection:
  - Convert the AI Answer into a Snapshot, then transform it into a sequence of Blocks ready for insertion.
   - Invoke the `replaceSelectedTextWithBlocks` command to replace the current selection with blocks (given the complexity of block combinations, this command uses [ts-pattern](https://github.com/gvergnaud/ts-pattern) implementation to ensure compile-time prevention of pattern handling omissions).
2. Optimized unit test assertions for commands, now allowing direct document content comparison using `toEqualDoc`.
```ts
const host = affine`
  <affine-page id="page">
    <affine-note id="note">
      <affine-paragraph id="paragraph-1">Hel<anchor />lo</affine-paragraph>
      <affine-paragraph id="paragraph-2">Wor<focus />ld</affine-paragraph>
    </affine-note>
  </affine-page>
`;

// ....

const expected = affine`
  <affine-page id="page">
    <affine-note id="note">
      <affine-paragraph id="paragraph-1">Hel111</affine-paragraph>
      <affine-code id="code"></affine-code>
      <affine-paragraph id="paragraph-2">222ld</affine-paragraph>
    </affine-note>
  </affine-page>
`;

expect(host.doc).toEqualDoc(expected.doc);
```
3. Added support for text cursors in unit test template syntax.

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

> CLOSE BS-3278

- **New Features**
  - Introduced the ability to replace selected text in documents with blocks, supporting advanced merging and insertion scenarios for various block types.
- **Bug Fixes**
  - Improved handling of text selection and cursor placement in document templates used for testing.
- **Tests**
  - Added comprehensive tests for replacing selected text with blocks, including edge cases and complex selection scenarios.
  - Enhanced test utilities for document structure comparison and selection handling.
  - Updated end-to-end tests to verify correct replacement of selected text via AI-driven actions.
- **Chores**
  - Added and updated dependencies to support new features.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/shared/package.json

@@ -44,6 +44,7 @@
     "remark-parse": "^11.0.0",
     "remark-stringify": "^11.0.0",
     "rxjs": "^7.8.1",
+    "ts-pattern": "^5.1.0",
     "unified": "^11.0.5",
     "unist-util-visit": "^5.0.0",
     "yjs": "^13.6.21",