Business Hours Block: include HTML in block editor

#### Steps to reproduce the issue

1. Go to Posts > Add New
2. Create a new post, including a business hours block.
3. Once published, the block will be displayed nicely on the frontend.

If however, you do one of the following, you will lose the actual HTML behind the block:
- View the post outside of WordPress, like in a subscription email.
- Try to edit the block's HTML code.
- Deactivate Jetpack.

Ideally, even if it does not keep the whole block's content, we should be able to offer an HTML fallback for this block. It should be more than just a block tag:

```

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Compare it with a map block for example, that includes some fallback info (a div with an unordered list of links to each marker):

```

```

Start in the Business Hours block editor and compare its saved and rendered output with the map block example, which includes fallback HTML. Check the published post, external rendering, and block HTML-editing paths; done means the business hours data still produces useful HTML outside the active block and when Jetpack is unavailable.

Written by the indexing model from the issue text.