[TabBarView] Animate text and icon colors when switching tabs.
[TabBarView] Animate text and icon colors when switching tabs.

The text and icon colors are expected to animate alongside the transition between selected tabs. This change moves the icon + font changes into the animation block, and adds a separate transition animation for UILabel's textColor because textColor is not implicitly animatable.

PiperOrigin-RevId: 326677877

material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios