Merge "wmshell: let shell init asynchronously" into main

    private class ShellInterfaceImpl implements ShellInterface {

        @Override

        public void onInit() {

            try {

                mMainExecutor.executeBlocking(() -> ShellController.this.handleInit());

            } catch (InterruptedException e) {

                throw new RuntimeException("Failed to initialize the Shell in 2s", e);

            }

            mMainExecutor.execute(ShellController.this::handleInit);

        }

        @Override