feat: add dedicated JavaScript thread support

[andycall]

RFC: openwebf/rfc#4

First version implemented by @penneryu and improved by @andycall

Use example:

DedicatedThreadGroup threadGroup = DedicatedThreadGroup();

WebF(
  bundle: WebFBundle.fromUrl('assets:assets/bundle.html'),
  runningThread: DedicatedThread(), //  Executes your JavaScript code in a dedicated thread
),
WebF(
  bundle: WebFBundle.fromUrl('assets:assets/bundle.html'),
  runningThread: FlutterUIThread(), // Executes your JavaScript code within the Flutter UI thread.
),
WebF(
  bundle: WebFBundle.fromUrl('assets:assets/bundle.html'),
  runningThread: FlutterUIThread(), // Multiple WebF instance in same thread supported.
),
_kraken = WebF(
  bundle: WebFBundle.fromUrl('assets:assets/bundle.html'),
  runningThread: threadGroup.slave(), // Executes multiple JavaScript contexts in a single thread.
),
WebF(
  bundle: WebFBundle.fromUrl('assets:assets/bundle.html'),
  runningThread: threadGroup.slave(), //  Executes multiple JavaScript contexts in a single thread.
),

Design Graph:

performance comparison:

Test devices: Moto Qingyou XT1799 arch: arm

Test code:

p.addEventListener('click', (e) => {
  e.data = { name: 1};
}, true);

p.addEventListener('click', (e) => {
  console.log(e.data);
}, false);