Revert appearance tools theme support

[poena]

The appearance tools theme support includes block gap, a feature that was not intended for themes without theme.json.

The feature does not work for themes without theme.json because they do not support layout settings and because of different HTML markup in the group block.

​https://github.com/WordPress/gutenberg/pull/47451#issuecomment-1411373956

Until it has been determined if the feature can and should be enabled in these themes,
and has been successfully tested, the appearance tools theme support should be reverted.

[Mamaduka]

I'm going to add a link to @poena's latest PRs. I think it summarized current problems with appearance-tools pretty well - ​https://github.com/WordPress/gutenberg/pull/47675#top.

[scruffian]

I think this is a good idea.

Reverts changes from ​https://github.com/WordPress/wordpress-develop/pull/3846. See the core ticket for more details.

Trac ticket: https://core.trac.wordpress.org/ticket/57649

Thanks for the super-fast response, @audrasjb ⚡

[jffng]

I agree based on the testing and feedback it makes sense to revert this. Classic themes still have a way get design tools via adding theme.json and opting in explicitly.

[davidbaumwald]

In 55273:

Themes: Revert appearance tools theme support.

The appearance tools theme support(merged in [55067]) includes block gap, a feature that was not intended for themes without a theme.json.

Until it has been determined if the feature can and should be enabled in these themes, and has been successfully tested, the appearance tools theme support should be reverted.

Reverts [55067].

Props poena, Mamaduka, audrasjb.
Fixes #57649.

This PR is an exact copy of reverting https://core.trac.wordpress.org/changeset/55076, and that was done on trunk in https://core.trac.wordpress.org/changeset/55273. Closing this PR as "merged".

Thank you, @dream-encode!

Thank you, @dream-encode!