Recover from server-side errors that may happen during rendering preview

Overview

When a server-side error occurs during rendering the content preview, there is no way to recover from it other than deleting tempstore, which can mean data loss. This usually happens when adding a problematic component to a page. E.g.: #3502371: Make "Page title block" work A) also outside regions, B) on the only routes XB currently supports: content entity routes.

Proposed resolution

The error is caught by an error boundary where we can define a callback to attempt a reset in order to recover from the error. Currently we rely on the default behavior which will re-render the React component tree. This won't help if the error keeps occurring with the layout and model already saved server-side. What we can do instead is dispatching an undo action, which will remove the last added component, or revert component input changes that may have broke rendering.

User interface changes

Change the label of the button on the error message to "Undo last action" from "Try again" to make it clear how the recovery will be attempted.