Allow exposed form for non-ajax block displays

Problem/Motivation

The block display doesn't allow exposed filters unless ajax is turned on. This seems to stem form Drupal 7 limitations. For a a view with facets to work the whole page should be refreshed, however.

Proposed resolution

Allow non-ajax blocks to have exposed filters.
This works because views always uses <current> route when view-URL/display-path is not available, for example: http://cgit.drupalcode.org/drupal/tree/core/modules/views/src/Form/Views...

Remaining tasks

Find cases where this would be problematic.
Write tests.

User interface changes

The exposed filters appear and the wtf-moment for site builders disappears.

API changes

none

Data model changes

none

Original Issue:

Exposed filters are getting lost, when view is rendered as block

If I'm creating a block which is based on the content view page (Drupal core view - ID "content"), then the view works except of the exposed filters, e.g. filter by title. You can see the view at the Drupal 8 site's URL /admin/content/node.

I'm displaying the block in my custom template. I'm getting the block markup by my following controller method:

  /**
   * Gets the HTML markup for a block by it's ID.
   *
   * @param $sBlockId The id of the block as string.
   *
   * @return string The HTML markup for the rendered block.
   */
  private function getBlockMarkupById($sBlockId)
  {
    $oBlock = \Drupal\block\Entity\Block::load($sBlockId);
    $aRenderArray = \Drupal::entityManager()
      ->getViewBuilder('block')
      ->view($oBlock);

    return \Drupal::service('renderer')->render($aRenderArray);
  }

Everything except the exposed filters is displayed. What's wrong?

I've also seen, that the exposed filters in block views are already a problem in previous versions of Drupal. See the related issues.