Save and restore view state for UIButton

[Juanpe]

Fix #309

Short description 📝

As @greatsk55 said, there is a problem when a button is skeletonizing. It seems the skeleton layer appears below the title label of the button.

Solution 📦

Before the skeleton appears, all views save their current view state to recover when the skeleton disappears. But some UI elements must override these methods because they require special behavior.

To solve this problem, we need to override the saveViewState and recoveryViewState methods for UIButton.
Also, when the skeleton is shown, we set the title value to nil and when the skeleton is hidden we retrieve the original title.

Implementation 👩‍💻👨‍💻

• Create a model to save the required view state for buttons. RecoverableButtonViewState.
• Create the UIButton extension to override the methods.
• Override the prepareViewForSkeleton method for UIButton, where we set the value of the title.