fix(editor): handle html content copied from google docs (#12383)

Closes: [BS-3508](https://linear.app/affine-design/issue/BS-3508/google-docs复制内容到affine时自动加粗问题)

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

- **New Features**
  - Improved detection of bold, italic, underline, and strike-through formatting in imported HTML, supporting both tags and inline CSS styles.
  - Enhanced handling of inline elements containing block-level children to ensure correct formatting and structure during HTML import.
  - Introduced a plugin that converts inline elements with block-level children into block elements, preserving original tag information.
- **Bug Fixes**
  - Resolved issues where block-level elements nested inside inline tags could cause incorrect formatting or structure.
- **Tests**
  - Added comprehensive test coverage for HTML formatting conversions and plugin behavior to ensure accuracy and reliability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/shared/src/__tests__/adapters/html/rehype-plugins/inline-to-block.unit.spec.ts

@@ -0,0 +1,61 @@
+import rehypeParse from 'rehype-parse';
+import rehypeStringify from 'rehype-stringify';
+import { unified } from 'unified';
+import { describe, expect, it } from 'vitest';
+
+import { rehypeInlineToBlock } from '../../../../adapters/html/rehype-plugins/inline-to-block';
+
+describe('rehypeInlineToBlock', () => {
+  const process = (html: string) => {
+    return unified()
+      .use(rehypeParse, { fragment: true })
+      .use(rehypeInlineToBlock)
+      .use(rehypeStringify)
+      .processSync(html)
+      .toString();
+  };
+
+  it('should not transform inline elements without block children', () => {
+    const input = '<b>Hello World</b>';
+    const output = process(input);
+    expect(output).toBe('<b>Hello World</b>');
+  });
+
+  it('should transform inline elements containing block children', () => {
+    const input = '<b><p>Hello World</p></b>';
+    const output = process(input);
+    expect(output).toBe('<div data-original-tag="b"><p>Hello World</p></div>');
+  });
+
+  it('should preserve existing attributes when transforming', () => {
+    const input = '<b class="test" id="demo"><p>Hello World</p></b>';
+    const output = process(input);
+    expect(output).toBe(
+      '<div class="test" id="demo" data-original-tag="b"><p>Hello World</p></div>'
+    );
+  });
+
+  it('should handle multiple block elements within inline element', () => {
+    const input = '<b><p>First</p><div>Second</div><h1>Third</h1></b>';
+    const output = process(input);
+    expect(output).toBe(
+      '<div data-original-tag="b"><p>First</p><div>Second</div><h1>Third</h1></div>'
+    );
+  });
+
+  it('should handle mixed content (text and block elements)', () => {
+    const input = '<b>Text before<p>Block element</p>Text after</b>';
+    const output = process(input);
+    expect(output).toBe(
+      '<div data-original-tag="b">Text before<p>Block element</p>Text after</div>'
+    );
+  });
+
+  it('should handle complex nested structures', () => {
+    const input = '<b><div><p>Nested <b>inline</b> content</p></div></b>';
+    const output = process(input);
+    expect(output).toBe(
+      '<div data-original-tag="b"><div><p>Nested <b>inline</b> content</p></div></div>'
+    );
+  });
+});