[MC-2263] Use weak reference check in controller hide

[nzagorchev]

Overview

• Use weak reference check in in-apps controller hideFromWindow: which dismisses the in-apps
• Mitigate potential crash on [CTInAppHTMLViewController hideFromWindow:]

Implementation

• Add a new method hideFromWindow:completion to CTInAppDisplayViewController which provides a completionBlock for hideFromWindow:
• Add weak reference check in hideFromWindow:
• Use the super hideFromWindow:completion in CTInAppHTMLViewController