Placeholder method to ViewRegion

[jhhazelaar]

Possible fix for #7820 and #6744.

[what-the-diff]

PR Summary

• Added a new method placeholder()
  A new method called placeholder() has been introduced.
• Modified the method's return value
  The return value of the method is now view($this->view, $this->context) for improved functionality.

[jasonvarga]

Thanks but this just makes the nocache tag do nothing when static caching is enabled.