Return early prior to evaluation of prop expressions if the user does not have access to the reference entity
## Problem statement
`\Drupal\canvas\Plugin\Canvas\ComponentSource\JsComponent::getExplicitInput` performs prop expression evaluation on entity reference props.
Inside the prop evaluation access control is checked.
However, we could do this in `\Drupal\canvas\Plugin\Canvas\ComponentSource\JsComponent::getExplicitInput` and return early, avoiding the overhead of the evaluation.
## Proposed resolution
Access check the referenced entity with `->access('view')` in `\Drupal\canvas\Plugin\Canvas\ComponentSource\JsComponent::getExplicitInput` and if it returns FALSE, return early.
issue