fix: UINavigationBarAppearance support for iOS15

[iamStephenFang]

Description

In iOS 15, UIKit has extended the usage of the scrollEdgeAppearance, which by default produces a transparent background, to all navigation bars." To restore the old look, you must adopt the new UINavigationBar appearance APIs.

Also see issue here.

Fixes # Navigation Bar Behaviors on iOS 15

Type of change

• [x] Bug fix

How Has This Been Tested?

• Previous Password UI

• Current Password UI

Test Configuration:

• Firmware version: PasscodeKit v1.0.1
• Hardware: iPhone SE 3rd gen Simulator
• Toolchain: Xcode & Lookin
• SDK: iOS 15.5

Checklist:

• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings