[skottie] Handle non-seekable streams

[mattleibow]

Description of Change

On Android, the streams for the Assets are not seekable - and the same with streams from the internet. So in order to actually read those, we first need to read the whole thing into a memory buffer.

This is not as expensive as it may sound as this is what happens internally. In C++, the full stream is read into a SKData instance, so pre-doing it in C# is the same thing. In fact, doing it via a data instance in C# opens up the potential to reduce the number of times we hop the interop boundary.

Bugs Fixed

None.

API Changes

class Animation {
  public static Animation? Create (SKData data);
  public static bool TryCreate (SKData data, out Animation? animation);
}

Behavioral Changes
Non-seekable streams can now be used to create animations.

Required skia PR

None.

PR Checklist

• Has tests (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Merged related skia PRs
• Changes adhere to coding standard
• Updated documentation