GH-2220: Onboarding - Telemetry

[benstrumeyer]

• Have you followed the guidelines in CONTRIBUTING.md?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you added an explanation of what your changes do?
• Does your submission pass tests?
• Did you lint your code prior to submission?

• Updates setup_step and pings gb_onboarding when a step is completed (specifically on the next button handler for each page)
• Pings gb_onboarding_success when clicking the Let's Search button on the Success screen
• Does not set the setup step for Step3_ChooseDefaultSearch as the page is not yet created (Left a TODO)
• Does not call setSetupStep() to update the conf value when the StepNavigation routes to a previous/next page. Should we handle this so users don't skip steps?
• Surrounds the shared-hub app with react-router so we can navigate using history.push('example-route')