Add the ability to customize the NUXButton styles on the Login Prologue

[emilylaguna]

WPiOS Related PR: wordpress-mobile/WordPress-iOS#16407

In order to achieve the design for the Jetpack Prologue screen I needed to be able to change the NUXButton style just for that view. But since the NUXButton relies on WordPressAuthenticator.shared.style this was not possible.

I updated the NUXButton to include a new NUXButtonStyle style struct that defines the 3 different states: normal, highlighted, and disabled. This uses an internal struct called ButtonStyle that groups the style into backgroundColor, borderColor, and titleColor .

I also added a new way to configure the style of the button, but will fallback to the "legacy" way if that is not used. This prevents the button from breaking for the other areas it is used in the app while adding new functionality.

Testing Steps

• You can follow the steps on the related PR
• Since this also can affect WCiOS, please also test there
• The NUXButton is used throughout WPiOS as well you can test the following locations:
  • Prepublishing bottom sheet
  • Domain registration view
  • Site Assembly

[frosty]

This looks great to me – I tested with the Jetpack PR, as well as a range of places in WPiOS where we use NUX buttons 👍