Migrate spec/javascripts/u2f/ to Jest

Description

Let's migrate the specs in spec/javascripts/u2f/ from Karma to Jest.

See the related epic for how to do this.

• spec/javascripts/u2f/register_spec.js
• spec/javascripts/u2f/authenticate_spec.js
• spec/javascripts/u2f/mock_u2f_device.js