feat(editor): by default render code iframe for html preview (#12848)

#### PR Dependency Tree


* **PR #12848** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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

- **New Features**
- Introduced a feature flag to enable or disable web container
functionality for code block previews.
- **Improvements**
- Code block HTML previews now support an alternative rendering method
based on the new feature flag, enhancing flexibility.
- **Chores**
- Updated feature flag settings by removing an obsolete flag and adding
the new web container flag.
- **Tests**
- Simplified code block preview tests for faster and more direct
validation of HTML preview content.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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

@@ -273,15 +273,6 @@ export const AFFINE_FLAGS = {
     configurable: isBetaBuild || isCanaryBuild,
     defaultState: false,
   },
-  enable_code_block_html_preview: {
-    category: 'affine',
-    displayName:
-      'com.affine.settings.workspace.experimental-features.enable-code-block-html-preview.name',
-    description:
-      'com.affine.settings.workspace.experimental-features.enable-code-block-html-preview.description',
-    configurable: isCanaryBuild,
-    defaultState: isCanaryBuild,
-  },
   enable_adapter_panel: {
     category: 'affine',
     displayName:
@@ -291,6 +282,14 @@ export const AFFINE_FLAGS = {
     configurable: isCanaryBuild,
     defaultState: false,
   },
+  enable_web_container: {
+    category: 'blocksuite',
+    bsFlag: 'enable_web_container',
+    displayName: 'Enable Web Container',
+    description: 'Enable web container for code block preview',
+    defaultState: false,
+    configurable: true,
+  },
 } satisfies { [key in string]: FlagInfo };
 
 // oxlint-disable-next-line no-redeclare