Embed block: Don't silently fail and convert to paragraph on simple sites.

Quick summary

A URL that can't be embedded will not throw an error, but silently convert to a paragraph block. This deviates from core behaviour.

Steps to reproduce

1. Create a post, page, or portfolio project on a simple site.
2. Try to embed a URL that won't embed. The user tried with this URL, and so did I. https://www.washingtonpost.com/brand-studio/wp/2021/11/05/celebrate-christmas-at-the-regions-best-holiday-destination/

What you expected to happen

WordPress should throw an error that it couldn't be embedded and give you either a retry option or to convert it to a link, as it does for atomic sites and in core.

What actually happened

The embed fails silently and is automatically converted to a link. The user is not told what happened or why.

Context

Reported in 35886495-hc, followed up in 5321519-zd-woothemes, tested by HE in chat and myself in ticket.

Simple, Atomic or both?

Simple

Theme-specific issue?

No response

Browser, operating system and other notes

No response

Reproducibility

Consistent

Severity

Some (< 50%)

Available workarounds?

No but the platform is still usable

Workaround details

Users will likely choose to convert it to a link regardless, but this became an interaction due to the lack of feedback. Converting it to a link, if silently, is better than stripping the failed embed.