Give Atomic and self-hosted sites the same comment toolbar as Simple

### Impacted plugin

Jetpack

### Quick summary

The `Enable blocks in comments` setting becomes unavailable when upgrading a Simple site to Atomic and blocks can no longer be used in comments. This creates an inconsistent user experience when upgrading. This possibly affects all current AT sites, but I am not sure. None of my test AT sites display the setting currently.

This user had various settings change when going AT, but I'm only filing a bug report related to Verbum for now: 8762683-zd-a8c

This same user also experienced an issue 2 months ago where comments did not display at all while their site was still Simple until disabling and enabling "Enable blocks in comments": p2EDhh-2iu-p2

### Steps to reproduce

1) Create a free site
2) Ensure `Enable blocks in comments` is enabled by default under Settings > Discussion
3) Upgrade to a Business plan and activate hosting features to go Atomic
4) Check Settings > Discussion or https://wordpress.com/settings/discussion/{siteurl} and see "Enable blocks in comments" is gone with no way to enable
5) Check comment forms on frontend and see blocks can't be used
6) Revert the site back to Simple and see the option return, allowing blocks to be used in comments again

### A clear and concise description of what you expected to happen.

Settings for comments should remain the same when upgrading a Simple site to Atomic.

### What actually happened

The settings change and become unavailable.

### Impact

Most (> 50%)

### Available workarounds?

No but the platform is still usable

### If the above answer is "Yes...", outline the workaround.

_No response_

### Platform (Simple and/or Atomic)

Atomic

### Logs or notes

_No response_

Reproduce the issue through Settings > Discussion and the frontend comment form while switching a site between Simple and Atomic. Trace how the “Enable blocks in comments” setting and comment toolbar differ between those states; done means the setting remains available after the upgrade and blocks work in comments as they do on Simple sites.

Written by the indexing model from the issue text.