Only add .layout-builder-block to blocks when in the Layout Builder UI

Problem/Motivation

\Drupal\layout_builder\EventSubscriber\BlockComponentRenderArray adds

'#attributes' => ['class' => ['layout-builder-block']],

to all blocks rendered by Layout Builder, regardless of whether it is for the Layout Builder UI or for the end user.

Proposed resolution

Only add for the Layout Builder UI.
Consider adding it in a wrapping div instead of altering the block directly

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet