Use Google's Prefab standard as format for Android prebuilds

[kraenhansen]

We're currently expecting Android prebuilds to be distributed as "jni-libs like" directories of architecture specific directories.

This has a few drawbacks:

• It doesn't provide an obvious way to distribute headers alongside the shared object files.
• It provides no way to distribute information on dependencies and STL ABI expected by the library.

These shortcomings are all address by Google's Prefab standard and I suggest we adopt this for React-Native Node-API prebuilds for Android.

[RobinWuu]

I like Prefab; it's a more modern standard.