WorkerSolver: Update worker solver to use a basic ArrayBuffer rather than SharedArrayBuffer

[gkjohnson]

SharedArrayBuffers are not always available on all platforms including Chrome on Android

[gkjohnson]

Not available in Safari, either, but they have been reenabled behind a flag in the latest technology preview. And it sounds like there's a plan to get them enabled again on Chrome Android.

Trading the buffers back and forth would be a bit complicated and performance may suffer a bit, as well. We could just transfer results the IK is converged? Or the solver can continue to iterate in the background while the buffer is transferred, applied, and then immediately transferred back.

[gkjohnson]

Instead we should automatically fall back ArrayBuffers and swap them back and forth:

const useSharedArrayBuffer = ( typeof SharedArrayBuffer ) !== 'undefined';