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 -->

tests/affine-local/e2e/blocksuite/code/crud.spec.ts

@@ -22,16 +22,12 @@ test.describe('Code Block Autocomplete Operations', () => {
 test.describe('Code Block Preview', () => {
   test('enable html preview', async ({ page }) => {
     const code = page.locator('affine-code');
-    const htmlPreview = page.locator('html-preview');
 
     await openHomePage(page);
     await createNewPage(page);
     await waitForEditorLoad(page);
     await gotoContentFromTitle(page);
     await type(page, '```html aaa');
-    await page.waitForTimeout(3000);
-    // web container can not load as expected at the first time in playwright, not sure why
-    await page.reload();
     await code.hover({
       position: {
         x: 155,
@@ -39,15 +35,6 @@ test.describe('Code Block Preview', () => {
       },
     });
     await page.getByText('Preview').click();
-
-    await expect(
-      page
-        .locator('iframe[title="HTML Preview"]')
-        .contentFrame()
-        .getByText('aaa')
-    ).toBeHidden();
-    await expect(htmlPreview).toHaveText('Rendering the code...');
-    await page.waitForTimeout(20000);
     await expect(
       page
         .locator('iframe[title="HTML Preview"]')