Add SwiftUI APIs for controlling playback behavior using LottiePlaybackMode

[calda]

This PR adds a new LottiePlaybackMode type, which we can use to add SwiftUI APIs for controlling the animation's playback behavior.

#2123 revealed an issue with the previous implementation approach using configure { ... }. Here's an example where the LottieView unexpectedly doesn't respect that the playback should be unexpectedly starts playing again. This was because looping() and currentProgress(...) were both adding a separate configure closure, which conflicted with eachother.

Instead, we should have a single property that is the source of truth for the animation playback configuration (playbackMode) which is set by both of these different APIs:

public func looping() -> Self {
  var copy = self
  copy.playbackMode = .fromProgress(0, toProgress: 1, loopMode: .loop)
  return copy
}

public func currentProgress(_ currentProgress: AnimationProgressTime?) -> Self {
  guard let currentProgress = currentProgress else { return self }
  var copy = self
  copy.playbackMode = .progress(currentProgress)
  return copy
}

This lets consumers express the current playback mode more fluently:

private var playbackMode: LottiePlaybackMode {
  if animationPlaying {
    return .fromProgress(playFromProgress, toProgress: playToProgress, loopMode: loopMode)
  } else {
    return .progress(sliderValue)
  }
}

This API also gives us an easy way to support playback modes other than just looping, so this PR also adds full parity with all of the playback options supported by LottieAnimationView.

Fixes #2123.

[miguel-jimenez-0529]

So cool

[miguel-jimenez-0529]

LGTM