[Bug]: `StyleManager.refreshAppearance(for:)` can break unrelated views

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### Mapbox Navigation SDK version

3.12.1

### Steps to reproduce

This behavior was originally introduced in https://github.com/mapbox/mapbox-navigation-ios/pull/519#discussion_r134604014

1. Create an app that doesn't immediately user MapBox screens
1. Add an arbitrary `UIView` to `UIWindow`
1. Create constraints between this view and the window
1. Instantiate `NavigationViewController`
1. Set `NavigationViewController.showsSpeedLimits = false`
1. This is going to cause `StyleManager.refreshAppearance(for:)` call

### Expected behavior

Arbitrary `UIView` is left untouched, still constrained to the `UIWindow`

### Actual behavior

Any unrelated `UIView` that is direct child of the `UIWindow` gets removed, losing the constraints, and re-added back to the window.

### Is this a one-time issue or a repeatable issue?

repeatable

Start at StyleManager.refreshAppearance(for:) and reproduce the issue by adding an arbitrary UIView with window constraints before instantiating NavigationViewController and setting showsSpeedLimits to false. Trace how the refresh handles direct UIWindow children; done means the unrelated view remains attached and its constraints are preserved.

Written by the indexing model from the issue text.