Deprecate and remove the AJAX replace method

Problem/Motivation

core/lib/Drupal/Core/Render/Element/RenderElement.php 

This looks like a Drupal 7 deprecation.

      // @todo Legacy support. Remove in Drupal 8.
      if (isset($settings['method']) && $settings['method'] == 'replace') {
        $settings['method'] = 'replaceWith';
      }

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet